All my machines - including my desktop - are 32 bit. This lone x86_64 machine is a headless server (well I plug in a monitor from time to time) - but usually its headless (as are all my machines but my desktop)...
All of our servers have been 64bit since '04 or '05? Whenever the first 64bit multi-core AMD chips came out and were under $300.
For a server, the big reason to go 64bit is capacity. While you might be running on a 2GB server today, it's quite possible that you'll move those disks to a 8/16/32GB server next year. If you didn't go 64bit at the start, you'd have to do the 32->64 move at the same time as hardware migration.
(Just as a hypothetical "for instance" example. May not occur frequently in real life.)
For desktop use, sounds like we're finally to the point where you can run 64bit Linux on the desktop and stay functional (i.e. Adobe Flash).