Spinervals are good, and very much like a spinning class. I think I have five discs and have used them a fair bit over the past few years. If you look on the Spinerval website you can view a demo of the footage. I have tended to go with the more aerobic base building discs. I kept an eye on ebay and managed to pick up a couple of discs at a bargain price.
I do prefer the Sufferfest videos, the music and footage is very good, but it normally is at 100% effort and leaves me in pieces at the end. My current favourite session is Fight Club followed by Revolver.
To get the most out of Spinervals or Sufferfest you will need a cadence sensor and a HRM.