> The other OSes we'd likely consider are FreeBSD, Linux (probably Red Hat),
> and Solaris. Any of these would likely do the trick, but I'd really very
> much rather run my OS of choice. :)

I would suggest that you NOT use Linux RedHat, not even version 5.1. 
Because of its wide dissemination and huge youth-type user base, there is
a large proportion of evil p rick s who specifically try to find
weaknesses in the OS itself. Straight out of the box, it is so wide open
that anyone who uses the default redhat configuration is asking for their
machine to be hacked/compromised/deleted. 

As a matter of fact, Linux kernels as recent as 2.0.33 can be completely
crashed (I get the "Aieee! Killing interrupt handler!" message..) by a
sufficiently determined attacker with access to a machine that can pass
itself off as any IP and has a fast internet link. (OC-3, or multiple
DS1.) I was witness to a number of crashes only just recently, on my
company test httpd apache server.. needless to say, I think I'm heading
towards OpenBSD/NetBSD as our main server system..

Given its track record with me, I will be the first to tell everyone that
RedHat is NOT the best choice for a "mission-critical" server unless it
isn't exposed to outside/high-speed data *attacks*. (Like aboard the Space
Shuttle.. :)

Anyhow, there's my $0.02 . I recommend NetBSD, even if there is a lot of
hardship getting things to compile on it. The extra work is a reasonable
trade-off IMHO.

ttyl,

Marc Tooley
tooleym@douglas.bc.ca