I was, until recently, a customer of EuroVPS, and I rented a CentOS VPS with 512 megs of RAM for 3 years. Because my services were growing more memory hungry over time, and my income were shrinking - I had to switch to another provider. Even though EuroVPS may not be the cheapest of them all, i can honestly say that I've been pleasantly surprised by their support staff. I've contacted them several times - with problems big and small - and each and every time I've gotten a respectful, insightful and always helpful answer. Sometimes, I've also gotten replies from them by e-mail in the middle of the night.
Of all the trouble I've had while I was a customer of EuroVPS, they were mostly my own fault - and they even helped me look in the right direction whenever i couldn't figure out what the problem was.
Oh, and if anyone wondered why i only reviewed their customer service; their VPS service always worked like it should (except for the times i messed up), so there's really not much more to say.
Thanks EuroVPS! Your service and customer service is A+! :-)