Does anyone use a 64 bit OS on their server?
 

Saw that my host is now offering much better hw for the same price, which includes 8GB of RAM. Unfortunately a standard 32 bit OS cannot use more than 4GB without nasty hacks like PAE.

I've had no problems with FreeBSD 7.0 64 bit in the office, but that's a fairly simple setup with only a couple of applications running... does anyone run Apache/PHP/mysql etc on a 64 bit OS?

I have a 64 bit OS on my server at Pacific Rack. CentOS 5 64 bit. We just upgraded it to the latest stable apache.php.mysql etc. and all is running fine.

What was the reason for choosing 64 bit?

The ability to add more RAM.

Thought so. I started fooling around with 64 bit both for the extra total RAM, and blowing away the per-process limits (which under FreeBSD 32 bit is 1GB max RAM allowed per process)