CentOS is basically the efforts a small development team that obtains the source code/files for Red Hat Enterprise and compiles them into their own distro. The idea in itself is sound, if you like using Red Hat.
From a server perspective, Red Hat is a very stable distribution, but I haven’t been that excited about using it for a desktop OS. For example, I keep a P3-based machine in my office just to use as a file storage server (within my LAN) currently running SuSE. If I wiped it clean and did a pure text-based CentOS install (I don’t use X on my file server), then it would be very similar to Red Hat and would likely run very well.
However, if I wanted to do anything more than just a simple Linux-based application like storing files, then it doesn’t take long for one of many other distros to catch up and surpass CentOS. Things like Windows networking, multimedia, and support are either commercially available or freely available through enthusiastic users.
So if I looked at it another way, it wouldn’t be that difficult to use Debian or Gentoo for the same file server. Hell, let’s just throw Fedora on it 
You get the picture – just my opinion.