I use Arch as my everyday OS but I've been developing a few sites with Django and Ruby on rails and wondering what OS would be best suited for a server environment.

I'm building a custom dedicated box as well I'm not going to spend hundreds of dollars per month for dedicated hosting in which if you know what you're doing you're better off on your own + it's free once you have your box.
I've used Gentoo, Arch, and SUSE(OpenSUSE) as OSs and Suse seems very stable as SLES is generally OpenSUSE with it's server tools but updates aren't as quick which is ideal for a server environment.

With Gentoo or Arch you have to constantly update every month or every week, with gentoo I don't want to deal with mainly because of it's compile times which offer..really nothing over arch in terms of performance and even stability at this point which begs the question. Is source compiling even worth it? Even compiling from source with Arch is 10X quicker then gentoo.

For Servers though I would consider Arch but the constant updating freaks me out as an IT, Gentoo makes me want to jump off the ledge, Suse, CentOS, Oracle Linux, or even RedHat have less frequent updates and are made for the server and oh forgot about CloudLinux(cheap compared to suse or redhat per year. 14/mo 168/yr.) I've heard good things about Cloud Linux as well.

For a server is Arch a good option?

I won't comment on being good, but there are 'better' options available for servers.
Regards.

Like what CentOS..

Yes. You know it already.

Regards.

That's a matter of opinion question. It depends on your requirements.

Many might say that Arch isn't suitable for a server because it is a rolling release. I haven't had any trouble to speak of with Arch, but rolling releases won't necessarily have the most stable versions of software.

For a server many would use
FreeBSD ( Not Linux)
Debian
Centos
RedHat, Oracle etc.

You'll have to update any of those of course. You can't get any simpler than
I haven't had any trouble with pacman at all, in fact it's one of Arch's best features. And now that packages are signed it's more suitable for enterprise. I update once a week. Pacman updates kernel and apps, although you will occasionally need to alter config files yourself. When kernel 3 rolled out a grub menu.lst mod was needed. If you look at the front page of Arch's web site, updating info is there. Read it before blindly updating.

My server runs FreeBSD but I don't see why Arch would not do the job. You'll lack the compiling options that you get with BSD, Debian, Gentoo if that's important to you. You can compile from source on an Arch box but pacman won't update it. There is yaourt now that suppose to take care of AUR. I haven't had any major problems with it in the last year.

Good luck whatever you choose.

I probably would not say as suited as Red Hat/Centos or Oracle but since I use it as my main OS it is to maintain but I wouldn't call it Enterprise Ready maybe one day someone will work on a enterprise LTS version of Arch but not today. Well, Arch is based off of Slackware so you can use slackware I guess.