I just switched from a $5 a month host who worked great for over 2 years. When my new blog hit is big time, they requested I leave because I kept crashing the server. I have not switched to Media Temple and I must say I am so happy with them.
I actually joined over the phone talking to a real person, no wait time, and no Indian accent on the other end of the phone. The control panel is pretty custom so it takes some getting use to, but I have love it after using it for a few days.
Check them out at http://www.MediaTemple.com