I've extensively used a lot of tablets, due to both longtime interest in mobile technology, and my line of work. To give you an idea of my frame of reference, I've either owned or used the following tablets: Ipad 2 (owned), HP Touchpad (owned - 2011 firesale!), Motorola Xoom / Galaxy Tab 10.1, LG G, original Asus Transformer (work). Heck, I've owned the following Windows Mobile / PocketPC devices from back in the day - HP Jornada, Toshiba e800. My phone is the iPhone 4.
With that said, this is one of the best tech gadget I've ever owned. The unanimous rave industry reviews (and very positive end user reviewers, even taking wifi issues etc. into account) aren't wrong.
* BUILD AND FORM FACTOR: evocative of but actually feels higher quality than the Ipad 2 and Macbook Air, which is a minor miracle at this price point. Beautifully machined aluminum, minimalist but not cold. The resolution of the screen is the best out of any current tablet, and can be crazily bright enough that it is useable outdoors in sunlight. It's definitely a fingerprint magnet though.
* COLOR - for those deciding between the gray or champagne, I received the champagne, and I actually called to confirm that I received the right one. It's much more silver than gold, it's basically silver aluminum with some gold highlights when the light catches it the right way. This is *exactly* what I wanted - it's reminiscent of the classic aluminum MacBook Pros, but with a touch of warmth from the gold. In short - it's not very gold at all.
* PROCESSOR - the Tegra 3 quad core processor is noticeably snappy, making the whole experience (even with Honeycomb) feel next gen. I've been getting great battery life, ~ 10-12 hours of normal mixed used, on balanced setting. With the dock, you're at 18+ hours. The NVIDIA fifth "stealth core" does its job seamlessly. It just works. For a quad core tablet with blazing power, this is again pretty mind-bending and next-gen. Is a quad core necessary? Strictly speaking, no. The Tegra 2 / OMAP / Snapdragon tablets do just fine, for the most part (although the un-overclocked Touchpad is noticeably slow), but every non ipad tablet lagged behind the iPad 2 in terms of real world performance (opening menus, browsing, launching apps). This isn't because Apple's processor is faster, but rather because if the sheer level of optimization between Apple hardware and software, which is industry-leading. With the Tegra 3 processor, though, this is the first non Apple tablet that both objectively is, and also noticeably feels, faster, more responsive, and more powerful than the iPad 2. It just brute forces past all of the Apple optimizations. For me, that is huge, especially if I'm going to be spending over $400 on something. Slowly but surely, more and more apps are optimizing for quad core (especially games), but even without that, I'd get a quad core for the general performance benefits alone, as it translates across every app.
* OS / SW - I really like the iOS UI for phones, it's simple yet powerful, but for a tablet it's always just felt incredibly limiting / frustrating / slightly condescending. I even prefer WebOS to it. Android Honeycomb is a nice balance between power, customization and being relatively easy to pick up, just perfect for the tablet form factor. My 2 year old toddler figured out how to use it in about 20 seconds (similar to WebOS and iOS). That being said, I'm looking forward to ICS, which should make things even more stable (HC still crashes occasionally)and uniform. The fact that the Prime gets an ICS in a month or two is fantastic. The pre-loaded Asus apps are relatively minimal and unobtrusive, and some actually are quite nice, such as the Asus cloud. Polaris Office is solid. The Android Market could be improved though, especially in terms of sorting and organization. Finding the right app can be a bit of a crapshoot.
CONS: Basically the same nits as others have pointed out.
* SPEAKER: the rear-facing speaker placement is a bit dumb, because it gets covered up relatively easily by your hands or when you set it down. However, you can still hear it even if it's completely covered, it's pretty loud, and it's located where the tablet tapers inwards so it doesn't get completely covered by a flat surface when setting it down. I don't mind the lack of a second speaker per se, as you hardly get stereo sound from any of the other tablets that have two speakers. I would say the sound quality of the Prime is on par with any other tablet, but it is just a bit easier to muffle. A jawbone jambox bluetooth speaker or the like works beautifully to supplement this tablet. It's certainly not needed, but it's a nice addition.
* CHARGER - the proprietary charger really annoys me. Until Asus comes out with more accessories, I'm basically stuck with using my one charging cord. Even charging via the dock requires the proprietary connector. It's not worth deducting a star for (at least for me), because it's more of an annoyance in light of how great the rest of the device is, but sheesh.
* PRODUCT LAUNCH - for a $21 billion company of 110,000+ employees, Asus still can't do a good product launch to save its life. This doesn't detract from the end product per se, but it's worth mentioning because so many pre-orders (on Amazon and elsewhere) were bungled or delayed. Asus is starting to consistently put out really great products, but in order to get to the "next level"(Sony, Apple etc.) in the eyes of the average consumer, they're going to really need to work on marketing and sales execution.
OVERALL: this thing is pretty ingenious, especially with the accessory dock / keyboard. Hopefully a harbinger of good things to come in the Android tablet space.
<<UPDATES AS OF 1/24/2012>>
These are discussed more in the comments, but I thought it would be useful to update the main review.
* ICS - I updated to ICS the first day it was out (good job Asus in pushing this out two days earlier), to absolutely no problems. It was like any other firmware update. The system notifies you that there's an update available, you tap yes, and voila. ~10 minutes later, ICS is installed. It's pretty seamless - no loss of applications or data. I haven't noticed wholesale differences, but everything is smoother, more streamlined, and sometimes faster. It's a definite plus. Asus has already provided multiple firmware updates (on top of ICS), which is a very good sign that this product is being actively supported.
* WiFi - it's been pretty definitively proven that an all-aluminum back-plate is not the best for enhancing WiFI signals. Asus attempted to make up for this via "antenna differentiation," a fancy way for saying that there are two antennas instead of one. In practice, mine has very good wifi reception up to about 25-30 feet from the router. Specific numbers: wifi analyzer average value of -50 to -60, and speedtest of up to 18mbps, exactly on par with my laptop. However, once you get really far away from the router (i.e. outside, or more than 75 feet from the router), the performance erodes at a higher rate than the comparison laptop (wifi analyzer -90). For my purposes, this is extremely useable, and I never noticed the supposedly weak wifi until I started doing actual tests out of curiosity. A lot of people have had luck with installing repeaters and / or more powerful routers, but I haven't needed to go that route. Asus has announced that they're making a new Transformer Prime variant, the 700T, due in a few months (supposedly). This one will have a different, non-metallic backplate, similar to the original Transformer (i.e. plastic). For me, I'm happy to sacrifice a slight amount of WiFi range for the distinctive spun-aluminum backplate; those who don't feel this way should perhaps wait for the 700T if they can.
* Dock - my champagne dock finally shipped yesterday, about a month after the actual tablet arrived. I can understand this somewhat if this device were sold out by the millions, but I don't think that that's the case (even though it looks like this tablet is, deservedly, a hit as far as Android tabs go). It's just an almost mind-bogglingly bad manufacturing / supply issue with Asus. It's like they make 10 at a time and call it a day. Hopefully it's just the first month hiccup - it looks like there are more docks (esp. the grey) among different retailers and that's a good sign. My original criticism stands though - Asus is insanely bad at product launches.
* Accessories - I ended up purchasing this MoKo(TM) Premium Quality Slim-Fit Folio Cover Case with built-in Multi-Angle Stand for Asus Eee Pad Transformer Prime TF201 10.1-Inch Android Tablet, and the Skinomi Techskin screen protector. The case is not as whiz-bang as some iPad cases - it's the same tired black pseudo leather, but it's cheap and it gets the job done in terms of functionality. The skin is ok but seems to, ironically, scratch easily. I've had better luck with Invisibleshield with past devices.
* Overall - I'm pleased to report that the tablet is still working great. After a month of use, I'd say what really sets it apart is the Tegra 3 quad core, which is an unadulterated good. I can't imagine using a tablet without one now. The form factor and build are great, but with the caveats noted above.