I like Spinervals quite a lot - for riding on a trainer anyways - I'd much rather be on the road! But they're great for winter.

The first two are a lot easier (especially #1 - Team Clydesdale) than the ones from #3 on up. I have #1 and 2, then several of the "competition" ones, and they are killer. I like having the slightly easier ones to fall back on for days when I'm feeling a bit less ambitious.

I haven't used the Chris Carmichael tapes so can't compare, but Spinervals give a great workout. You will sweat, and they are better than just grinding away on your own since the intervals, out of saddle portions, super-high cadence portions, etc, really force you to push past your comfort zone, then recover.

Emily