EDIT: Still enjoying this machine after more than 1 year. I tend to use it at least once a week for fish. I also occasionally use it for (not-so-good) steak. Oh, and it excels at leg of lamb. I do want to note that the difference between tenderness and juiciness has never been more apparent to me than when I used this device - there's a reason it's recommended to serve sous vide meat with a sauce or jus. I note that there is a sous vide machine available through Amazon that's about half the size and half the price. I've never used it, but it looks like it might be a way to try this method of cooking without spending a fortune, although I question if the size is large enough for a small family. Finally, there's an excellent comment about cooking meat to two different levels of doneness in the comments section that I encourage you to check out...
This review is for the SousVide Supreme Demi. I've never seen or used the larger Supreme model, which is about 50% more expensive, for a slightly larger capacity. My understanding is that you probably get 1/3rd more space for the money. The only difference appears to be capacity, so this review may still be useful to read. See my warning at the end for what the machine won't do, but to be clear: you'll need to buy or already own a separate device that will allow you to vacuum seal food in plastic bags. This "oven" can't be used without that sealer and it's not included in this package, although certain warehouse stores have been known to sell a bundle that includes a sealer for not too much more money.
I will not claim to be an expert at SousVide cooking, but this seems to do exactly what you'd want. Briefly, what you'd want is a very precisely controlled water bath. The idea is that the food is put into a bag and vacuum-packed using a separate device, and then thrown into this "oven" to be brought to its perfect final eating temperature. Since there's no risk of over-cooking, food can be left in this state for relatively long periods of time: from hours to days. It is a great way of cooking steaks, fish, soft-boiled eggs/custards, and certain vegetables. It is not necessarily a faster way of cooking, nor does it seem optimized for the vast majority of baking applications. Note that you can't cook at two different temperatures without two different ovens, so you're probably either cooking meat/fish OR vegetables. Given the length of time it takes to cook foods, you probably wouldn't be doing both.
So, it's a device for holding water at a constant temperature for an indefinite period of time. Does this model do the trick? In a word, yes.
First, it is completely silent. There's not even a fan whirring gently in the background. There's not even the whine from the small LCD display. It's silent.
Second, it holds the temperature of the water plus or minus a degree or two (fahrenheit). You can set the temperature to display in celsius or fahrenheit. It relies entirely on convection to circulate the water (no blades or pumps to break) but that seems to work pretty well. Every time I reached into the water, it felt evenly hot throughout. Since one tends to cook things for long periods of time in one of these "ovens", I think convection works just fine. There is a timer that counts down time and then turns OFF the oven. Sadly, there is no count down timer to count down time and then turn the oven on.
Third, it comes up to temperature very quickly - from water out of the tap to cooking temperature in less than 15 minutes. Since you're cooking for long periods of time, you can probably ignore the warm-up and just throw your food in after you plug it in. The one cautiion here is that it takes a full three seconds of pressing the button before the power turns on. Three seconds does not sound like a long time, but it will stop the machine from being switched on or off by mistake. It sure feels like a long time when you plug it in for the first time.
Fourth, the capacity seems fine for anything up to a small family/6 people. If you're going to use it for entertaining or more than 6 people, you'll need the bigger model. I could fit six steaks into the oven. If you were really careful, and the pieces were small, you could probably fit 8. In terms of size, you can get the dimensions from the specs above, but it seemed like it would take a couple of small whole fish, or 6 inch-thick salmon steaks. Again, not great for big families.
Fifth, the lid and (optional) heat mat (which looks/feels like a mousepad) do a nice job of conserving heat in the unit. There's no steam and water at 130 degrees F, for medium-rare meat, just isn't that warm. I'm pretty happy reaching in and grabbing things without gloves or tongs. It's definitely warmer than a hot-tub, but no-one's going to get badly scalded. I'm not sure how high it will heat: up to 200 degrees F should be possible. I don't think it will boil water, but I've never tried. Certainly, that's not the point of this device, since the lid does not lock so it will never function as a pressure cooker. And if you wanted to boil food, you could do that in any pot.
Sixth, at the end, it's easy to take off the lid, pull out the tray, and use the two off-set handles to pick the whole thing up and empty out the water. You don't want this water sitting around for repeated runs - things will start to grow in it unless you add some salt or perhaps a copper penny or two. By the way, I'm sure that either of those approaches will invalidate the warranty.
Yes, this is basically a super accurate, very expensive crock-pot that's designed to be used with water and bags of meat instead of stew. Advantages: the meat will retain it's shape and consistency much better when cooked in the bag.
Ok, so what doesn't this product do?
Well, in order to cook food in this gizmo, you really have to buy a SEPARATE vacuum sealer and then a supply of bags. The sealer creates a vacuum inside special food-safe bags and then melts it closed. Note that the bags are not really re-usable and regular zip locks won't really do the trick, so you'll have to buy a supply of bags OR rolls of plastic that you can seal to create bags. The SousVide company makes a sealer (which I bought) that is not cheap, but that's because it has an important extra functionality: Some vacuum sealers will only seal the bag after a vacuum has formed completely. That will suck out any marinade/juices from the food. However, the SousVide sealer (and certain others, eg some FoodSaver models) allow you to seal the bag, independently of applying a vacuum. In this case, that means I can apply a vacuum until I see the marinade beginning to be sucked out, then hit the other button to seal the bag immediately. It works really quite well.
That's it. So why only four stars? Well, it's really expensive for what it is: a very nicely built waterbath. As an ex-scientist, I've used these in a laboratory setting and I couldn't find one cheaper ... but that's not really surprising since scientists get ripped off anyway. Basically, you're paying for being an early adopter. As these become more mainstream, I would expect the price to go down. Until then, c'est la vide (couldn't resist).