I noticed the age of the stock CentOS kernel the other day when trying to build something that used timer FDs - 2.6.18 was released in 2006.

To be fair, CentOS 6.1 is current - and has a "continuous release" repository too.

But those (like me) running old installs on CentOS 4.x are pretty much stuck though unless they are running fully dedicated and can do an unofficial upgrade (tricky stuff).

The "continuous release" repository provides individual updates from RHEL 6.2 as CentOS finishes repackaging them, rather than requiring you to wait until they've repackaged all of them. It still won't get you a kernel newer than (a heavily-patched) 2.6.32 from 2009.

Yep, this server is stuck on CentOS 5.5, which is apparently the latest the host offers.

I'm glad the new version uses a current kernel - I (naively) assumed that as the server was set up recently, the version of CentOS installed would be the newest one.

What are your requirements? There are a couple good VPS providers out there that offer up-to-date OS options. Look at Linode if you haven't already. (They've added London and Tokyo datacenters in the recent past, so if geography was a factor those might help.)

You can actually run unofficial/custom images on Linode with the pvgrub bootloader, too, though of course it's a little more work. People have even been running FreeBSD.

If you're going to experiment with this make sure you look at things like MTU as well, those are not always set to the optimal size for your link. If you have a high latency link in there somewhere (say you're in the mountains in Colorado and your only way to go online is through a satellite link) then this really starts to matter.