My main complaint is that XP has the familiar file search dialog (window like) box that is easy to use with lots of useful features, W7 has a moron text search box with one or two cryptic controls, and you have to do a full filename search before it gives you a 'search for text inside file' option. . I hate it.
but W7 (and W8) have a built in recorder so you can create audio files from the speaker sound lines, great for recording songs from online stations.
W8 is even LESS control friendly and more idiot appealing I suppose, and like Rusty notes it does stuff you dont want it to.
I try to move a window out of the way of another (to see both) with cursor and it maximizes it on its own blocking all the others, about five times before it does what I want..
Its like a gun that goes off based on sounds.
Try upgrading a thousand computers with hundreds of custom applications (and god knows how many private things people sneak in behind the techies backs).