I wouldn't say it runs faster becuase you'd be hard pressed to really demonstrate a performance difference between x64 and a 32bit version of XP.
I like it and it does feel less "buggy"... if that's the term you want to use.
What I have found is that most computer "bugs" are from the users doing or changing things they shouldn't have. Doesn't matter if it's Windows xx or any flavor of unix.
There are plenty of programs that don't like x64, but there are plenty that do. In the short time I've had with x64, I've noticed that when programs do crash, they are far less likely to take the OS down with them.
As far as viruses go, it is still infectible. I think the only way you could change that would be to elliminate the WoW64 sub-system. But that in and of itself would make the OS virtually un-usable due to lack of native 64bit programs.
The advantage x64 does have over viruses and the like is if you use the 64bit version of IE, all of the crap that can damage your system through ActiveX get's snuffed out before it can even try.
At the same time, this will also put a cramp in your web-browsing experiance as a whole. For instance, you still need to use the 32bit version of IE to go and use the Windows Update web site.
There is and always will be trade-offs, even when people start moving to Vista, you will still sacrifice somethings you have gotten used to, but will (at-least eventually) gain them back, if not in a better or different way.