I have been using https://www.atum.com for years. I was with Amazon, it just didn't cut it for my needs. We have a lot of ram and disk requirements, I found the IO/RAM to be quite bad.
I used Linode for a while, they were quite good as well. I went to Atum mainly because of a friend who was with them, had good things to say about the performance. I have a lot of customers in Canada and that is where there datacenter is because of the patriot act, it had to be in Canada so. Atum VPS has been great so far to me =)
