Like Jimbo and most others, I think 7 is a step in the right direction from the train wreck called Vista. It is however, in general, a much too small a step. Now, all you readers must understand that this thread is about what needs improvement (what we DON"T like) and therefore will, by nature, have a negative tone.
1) The big, HUGE thing (biggest single item) that I hate about 7 (and Vista) is the way it handles saved files and folders. XP started a downhill spiral when they combined documents and settings into a simgle directory. Vista went way downhill from there and 7 has made no significant improvement over Vista.
2) Next, I hate that they do not offer an option to totally disable the multi-user capabilities for those of us who are the sole users of our computers. Home group should also be able to be disabled, or to be made to work with two or three previous OS's. It only works with another Windows 7 system and can only be helpful to a large audience after a couple of years as Windows 7 becomes mainstream. There are enough of us who are the sole user of our computers that we should be heard and not have to wade through all the multi-user provisions to access a file. I do not need a user, all users, owner, owner gateway, administrator, default user, and maybe one or two other users on my computer.
3) I hate that they have made some things harder to locate by requiring more mouse clicks to open an application or website. This is carried over from Office 2007 and Vista.
4) This should be #2 in my priority list! I hate that AERO, gadgets, and a couple of other items cannot be TOTALLY disabled so they do not consume any computer resources. Neither storage nor memory. I am an "old fart" who just doesn't need or want any of the "Fluff and Puff" that does nothing to make my computer do what I want it to do, but consumes hige resources while doing NOTHING for me
I hate that, so far, I really do not see any improvement over Windows 2000, Windows XP, or enough improvement over Windows Vista to make me want to run out and spend something well into 4 digits to convert all 8 of my computers to Windows 7. Hopefully, this may change by the time Windows 7 goes prime time.