Also be aware that many software programs will see x64 as 2003 server which means they may not install. For instance if you use the free version of AVG anti-virus you will have to buy the pro version to use it on x64. Other programs will work but only with slightly older versions for one reason or another. So if you are highly dependent on a specific piece of software do some research on that with x64 before you make the jump to it.
On the other hand for most games and things of that nature work just fine for me on x64.
Edit: Also not sure if this is still a issue but if you use windows media connect to stream music or video to say an xbox360 it works quite a bit different on x64 than I have seen on 32-bit. But I have not seen a recent release on 32-bit at some point it got integrated into media player on x64.
Edited by Lidan, 09 April 2008 - 07:34 PM.