There are still a few rough edges to work out in Advancemame32 mainly around video card support - other than that it's perfect
If you are using and arcadeVGA you will be fine, if you are using anything else you may have an exciting time. Many video cards that work perfectly in DOS need a bit of tweaking for the windows version.
Key issues that I have come across are
Low pclock support is not good in windows, for example my geforce4 4200 can do a pclock as low as 5 in DOS, but can't go below 14 in wondows. You can get around this by setting the pclock divider/multiplier on.
Interlace mode supor tis not as good. many cards that support interlaced modes in dos doe not support them in windows. This can be a real pain if you want to play verticle games on a horizintal monitor. Only way arround this so far is to get a new video card
Other than those minor issues it works great!