benefit from 64-bit now...
Most games are designed for 32-bit and may have problems on 64-bit platform.
Sorry for the late reply, but: The opposite of what you say is equally true.
Some games burn a lot of user memory and can hit the 2GB ceiling enforced by 32-bit Windows. 64-bit Windows will in many cases double the limit for 32-bit processes and give these games (and apps) more room to grow... (see
http://www.anandtech.com/gadgets/showdoc.aspx?i=3034 for a longwinded discussion on this topic)
Note that this is virtual memory. It matters little whether you have 1GB physical memory or 4GB. (although, as you get more than 3GB physical memory combined with the latest powerful graphics card, you'll need to use 64-bit Windows so you can utilize all of your memory -- again, see the article above)
As for games, the biggest problem is shoddy copy protection schemes. Most (if not all) of them have been patched to support x64, but not all games have released patches with upgraded copy protection code. (stupid, but true: You buy a game and you only own it for a limited time -- don't plan on any hw or OS upgrades unless you get your hands on a pirated version)
--
Rune