I have used Suse 9.2 - a free version i got of a computer mag. The problems i had were that it didnt have all the packages i wanted/needed, like apache web server, php etc.. and to actually download and install the RPM's from the suse ftp was a real head f**k.. i basically gave up after a day or two as i would try to install something, but there would be an error as it depended on another package, and so on..
But saying all that i have been using different versions of Mandrake linux for a few years as a server, user shares, email and web, without any problems, and the webmin works great and makes it easy to change things - eg: create new users, samba shares etc. And its all been free, except for my time to setup and configure.
I couldnt use mandrake this time because i couldnt get it to work with my network card, so tried Suse instead, which configured network card fine, but then i had the problems with RPM's..
I also use windows 2003 server, is ok, but its expensive to buy. Is easy to setup, and also the interface is known by anyone who has already used windows.
The biggest problems i have had with windows servers is having to reboot every couple of weeks, or in one case with 64 servers every night as they would just get slower and slower if not rebooted... memory leaks i think.
So if the suse version you have has everything you want on it, or you are willing to install additional software, and you have the time, and willingness to learn - go with that...