I had gotten to the point where I was more than comfortable with Windows XP. It was solid and reliable. I could count on it. I'd tried Vista, at least the beta and Release Candidates, and had decided to hold off on purchasing - not uncommon, and with the massive underlying architecture changes, generally a wise choice. (The old "Never buy a .0 release" is still good advice.)
Recommend this product?
Well, Vista was a learning experience for everyone, and apparently Microsoft learned its lessons well. Even in the first (public) beta, I was impressed enough to say "I'd buy this right now, if I could" - something I rarely say about a beta. I preordered almost as soon as the option was there.
Yes, Windows 7 is built on Vista underpinnings, but it performs incredibly well. It's certainly not "just eye candy," though some features (Flip 3d) could qualify. There are great usability changes, from a finer-grained UAC (more than just on and off, encouraging you to maintain the protection it can help provide) to jump lists, Aero Snap - which is exceedingly useful, especially on today's common widescreen monitors, Gadgets that can be put anywhere, and good, solid 64 bit support. (Note there's still a limitation in the Home Premium edition of 16 Gb, up to 192 in Pro and above.) The Anytime Upgrade upgrades you directly between versions - no reinstall needed, just a feature unlock. Networking? Wireless (and wired) set up easily, network maps let you see what's out there, and Homegroups are so easy to set up an adult could do it. (Kids these days...)
Now, for upgrading, there ARE things to be aware of. From XP, you must do a clean upgrade - the changes underneath are massive. From Vista, you can do a direct upgrade from x86 to x86, or x64 to x64, but not across (x86 to x64 requires a clean upgrade) - so back up your data. The installation itself is incredibly fast and easy.
This is, quite frankly, the first version of Windows I've been happy to run, that I've looked forward to installing, and that I've recommended wholeheartedly to friends and relatives.