64 bit OS

Is there any real reason to have a 64-bit OS installed? I've been using them for months, I don't really notice a performance increase on the few 64-bit apps I have, but I do notice that I can't run any 16-bit installers.

>>1
Sucky Windows is sure sucky.
On server side a proper 64-bit Unix is groovy though.

On desktop you'll have best results with 64-bit kernel and 32-bit userspace for now (cos of proprietary software).