This product is only for computers running Windows 7 Starter, so if you are hoping to upgrade from XP or Vista with this kit you are out of luck. If you bought a Windows 7 netbook, chances are you have Windows 7 Starter and have already noticed a few shortcomings of the "netbook-friendly" OS. Among those are the inability to change the background or theme without assistance of 3rd party software, no Windows Media Center, and lack of Aero enhancements such as Glass (translucent borders) and Peek (thumbnail previews of open windows). Starter also lacks a 64-bit version and caps memory at 2GB, but the Atom processors in most netbooks are 32-bit and only support up to 2GB RAM.
Windows Anytime Upgrade is a convenient way to increase functionality without spending extra on a full upgrade kit. The case contains only a product key, no disc, so no external DVD drive is needed. Windows 7 installs all of the components for all versions regardless of which is being installed, locking features to all but their respective variant. This means that there is nothing extra to be installed and allows for the entire upgrade to finish in roughly 10 minutes.
The biggest problem with the Anytime Upgrade is that it can only be used to go from Starter to Home Premium. With regular upgrade packs, you can move to a particular flavor of Windows 7 from Vista, XP, or a lesser version of 7. If you wanted to, you could revert to your previous Vista/XP/7 and use the upgrade on another eligible computer. For a savings of roughly $40, you lose a lot of flexibility. If you decide to transfer the upgrade license, it has to be to another computer running Windows 7 Starter. [Note: I have not tested to see if you even can transfer an AU license, but a regular upgrade can be moved]
Bottom Line: If you missed out on the upgrade kit preorder sale, this is the cheapest way to upgrade your netbook to fully-fledged Windows 7 and take advantage of some of the new features. The fast, painless installation is perfect for netbooks preloaded with Windows 7 Starter, but useless for anything else.
---NOTE FOR TABLET USERS: Microsoft has available for download a package for multitouch display devices that is only supported in Windows 7 Home Premium or higher. If your tablet comes preloaded with Starter, you will not be able to install that update. If your netbook falls into this category, then this Anytime Upgrade comes with a stronger recommendation as it allows far more natural interaction that is otherwise severely limited without.
---EDIT: According to the license agreement, if you use an Anytime Upgrade (not a retail upgrade) on a computer, the license is inherited from the previous OS. If you AU an OEM build, the kind that comes preinstalled on retail computers, the AU is now an OEM product and not transferable to a new computer. HOWEVER, that does not mean that if your netbook breaks, your upgrade is lost forever. As long as the base hardware (read: motherboard) on a replacement is the same model as the original, it should work. This is based strictly on the licensing agreement; I have not tested to confirm.
---EDIT 7-09-2010: I finally had the need to test out the transfer of an Anytime Upgrade license and I can confirm the above. Since Windows 7 Starter edition only comes with an OEM license, ANY upgrades (AU, Upgrade, or retail pack used as an AU) to it inherit that OEM license and cannot be transferred from one computer to another. Use caution when using any form of upgrade with Windows 7 Starter. That said, this is the cheapest option to upgrade Starter to a full version, so if you are going to lock in that upgrade, no sense wasting the extra money on a more expensive set that will provide the exact same results.