I finally just moved to 64 bit on this box. I held out coz I was worried about certain compatibility issues. It's working, but there are hassles and I'm tempted to go back 32 bit
Lots of little things, like whether you have 64 bit (older) or 32 bit (latest) firefox - and what plugins to use... Now where was that 32 bit java...
Making sure you compile in 32 bit emulation in the kernel
A lot of the extra packages I have are 32bit, so I'm out looking for 64 bit replacements...
But it's going and I have 32 bit native games running as well as 32 bit cedega and 32 bit crossover. And 32 bit firefox 1.5...
No noticeable performance difference. My main reason for shifting was just to get used to the 64bit platform and it's going to be all that way soon, so I guess it worth shifting some time...
I still don't have win4lin going, but no big deal. I might have a go at that when they bring out a 2.6.15.x patch...
As for the fc4 install. You would get some performance tweak even if you just compile the kernel for a64 in 32 bit. Use some more instructions and registers... I was already doing that in 32 bit, so I probably notice less difference going to 64bit... See you are running old i386 instructions rather than i686 or better...
The memory issue in 64 is nice... No stuffing arround with the various memory models...