The feel of the OS is different overall. I can't say I like it, but there are some parts that I can get used to and some parts that will drive me up the wall. I want to slim it down enough to get it working everywhere. As I said, the VM is a replica of my EeePC's SSDs and RAM, so it should be an accurate representation of which vLite'd installations will work and which ones won't.
Anyways--this goes for any OS. If you're worried about losing a noticeable amount of performance, the upgrade is not for you. Supposedly, Windows 7 is faster than XP or Vista. I can't confirm that.