I don't know how high of a priority the basic controls (buttons, edit boxes, static, etc) are, but they sure do have a lot of FIXMEs that I'd be willing to help with. Mainly things that the writers didn't know what windoze did. I could probably fix a lot of these. I have a windoze machine, and I could tinker with it to find out the correct behaviour.
The only thing is that I'm relatively new to editing wine's sources, and extremely new to CVS, so I wouldn't know what to do with the code when I've finished. If someone could clue me in, I'd be more than happy to clean up some of the FIXMEs.