Redhat / Fedora - simply because I got involved with Linux with Redhat 5 when SCO decided to start charging for their OS on a user licence basis. When RH8 was released I bit the bullet and moved my clients servers over and have never looked back. I now have a mix of RHE and Fedora 3 thru 5 out there and a client base that is rapidly moving to Linux on the desktop as well.

I should add that another local S/W shop went with SUSE at about the same time and are as happy with their decision as I am with mine.

So different strokes for different folks and we seem to stick with what we are familiar with.