I am using both slackware current x86 and x86_64 theses are checked updated daily.
The x86 build seems so much more stable in the kde environment.
Linux bicycle 184.108.40.206 #2 SMP Sun Oct 10 20:05:32 CDT 2010 x86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ AuthenticAMD GNU/Linux 2 gig's of ram. NV GT9400 and Gt9600 graphic cards.
the system as of the 01-02-2011 updates both systems are very stable but the x86_64 always seems or has kde blips. like phonon and . I am a huge fan of the x86_64 system and use it most of the time. But the x86 build has given me less glitches.
That all said and done they are both very stable and top shelf in my book.
Any other people noticed this in some of the builds chime in.