User reviews are definitely the best thing to look out for. With any host your going to find some bad reviews, but when choosing a host just make sure the good reviews outweigh the bad ones. Also make sure the host is suitable for your needs. This includes reading the ToS/AUP for the types of sites allowed. you can read some reviews about vpswebserver here hosting.reviewsgurus.com/reviews/vpswebserver-253.aspx
Find a host that gives you what you need.
Also find a host that will give you real support.Not 24/7 , Just the support to help you solve any problem that you have when you need them.