Here is some hard truth for everyone...
Windows and Unix/Linux servers are only reliable as their adminstrators.
I worked with a Telcom and the Unix/Red Hat Linux servers always having issues, etc. But the Windows Servers had 99% up time and ran like champs. We even moved all our Java apps to windows cause dealing with the Unix admins wasn't worth it - they where so uptight about everything to the point you couldn't do your job.
Then when I left the Telcom to work with a Waste Management company - the opposite was going on - Unix/Linux boxes ran the databases great - but the servers running MS Exchange, IIS, applications, etc always had issues and forget keeping citrix up with out schedule reboots!
So I am sure given the right idiot admin and any Server OS can suck...
From my experience , the only server OS I have never seen issues out of was OpenVMS. You set that damn thing and could forget about it for years!