I've been using hosting on WHB for several years and must admit that it's not been WPS. However, I've had ZERO problems and ZERO need to contact their support. Is that a good referral or not? IMHO, that's excellent but leave me without any timing on response. Therefore, I believe that a test is in order: E-mail their support team with a question about their management, their update schedule, their default control panel (cPanel is extra), etc. Obviously, pick something that you need to know before switching and that only a techie can answer for you and their response time will tell you that little bit more than I can.
I've seen that Silver VPS and, because it offers so much more than my old VPS account with another host (except cPanel), I'm about to make the move myself!
Disclosure: Because of my long-term status as a client, WHB has asked that I let others know of my experience with them and have labeled it "Ambassador." It is UNPAID and I can assure you that you'd know if I ever had a problem!