I personally use 64bit but I don't game that much. I see no benefit of 64bit over 32bit besides some very minor program incompatabilities in xp64 (Macromedia FlashPaper for example).
XP64 is great if what you want supports it.
Users here have attested that XP64 feels more responsive and is faster for quite a few things.
Some programs/games dont work on XP64 and there is limited driver support.
You could get lucky with the drivers or find a forum that can help get you something compatible.
This page lists 64bit compatible and 64bit Native games: http://www.start64.com/index.php?option=com_content&task=view&id=190
Check out the rest of their site too.
The forums opened 3 days ago by the looks of it so there isnt any value there yet.
Maybe you can make the first post lol
It would be good to hear from XP64 users about what doesnt work.