I tried Suse 11.1 64-bit and could not discern any advantage over the 32-bit version. Am I missing something?

Both version have bugs, possibly related to my GIGABYTE MB and AMD tri-core CPU.

For example I had to #-out the "Virtual" lines in the file /etc/X11/xorg.conf to avoid booting to a virtual screen.

Any comments?

well to tell you the truth 64 bit means that it works with chunks of 64 bit memory instruction instead of 32 bit. New hardware today like ddr3 ram that will use the 64 bit instruction to the fullest. the same with your programs. But I see no need to run suse. just not a big fan of it I find it rather slow for 64 bit O/S must be their custom kernel. anyway that it the ability to have your hardware use 64 bit and to have the software use the benifits of a 64 bit cpu's. Why it has to do with the transfer of memory at x86_64 now you can write programs with 64 bit instructions in stead of 32bit. larger yet faster programs because of 64 bit memory allocations.
Hope this helps. On slackware 13 current I can tell the difference in the kde4 environment