We switched our VPS hosting over to
KnownHost.com, and that was the best move we have ever made other than switching from UBB to vBulletin.
Service has been incredible, 24/7 support and I don't think we've ever had a support ticket not answered in under 15 minutes. We have semi-managed accounts, and I needed to install Zend Optimizer on one of the servers we had, and asked support which version (there was something like 15) I should download and install. I was looking for advice and abou 10 minutes later I got an E-mail saying they had just downloaded and installed it for us...I was stunned.
You can also go over to
WebHostingTalk.com forums and look them up to see reviews by some of their peers over there.