I add drivers to graphics card, and anything else that is newer than what is on the Apple OEM DVD.
Some people have had trouble with trackpad if you look around.
If it ain't broke, don't fix it, but do create restore point; and do use Windows 7 built in backup for files and system image; might also want to use WinClone to image your Windows partition (runs in OS X).
Between applications, controllers, plug-ins, AV software (very difficult to find what works and what you want as not all of the recommended are problem free, and most all of the "W7" betas are even worse).
If you have trouble with a device, with network or wireless.
And when you want suggestions, we need more than "messed around" and "confused." Nvidia does have mobile graphics drivers, but probably not tested for W7 but a lot of people use 181.xx.
W7 RC in a couple months should be a whole lot better.
Upgrading to W7 over Vista SP1 sometimes works, sometimes not.
And there are forums devoted just to Windows 7.
http://windows7forums.com/