I'll share just because I think my experiences are different than most.
I've taken yoga from 3 different instructors in person, and tried a couple of DVDs, and I didn't like any of it. One was vinyasa, another was a beginner class where I think they mixed various forms, and the other was back in high school and I don't even remember, heh. Every instructor was too "spiritual" for my taste. Either that or they were always throwing out a lot of pseudoscience that makes me REALLY uncomfortable. I actually took one pilates class where the instructor was the same way - to the point where she was blatantly anti-science on occasion - so it's nothing against yoga, just a personality I can't really deal with (and certainly don't want to PAY MONEY to deal with).
I guess I do have some trouble being told what to think, which was an integral part of all the yoga workouts I've done. I understand the idea, but it makes me anxious and rebellious. You can tell me how/where/when to move my body, but I'd like to think about whatever I'd like, thankyouverymuch. So, part of the problem is me, I suppose.

I guess I wouldn't be a good target for hypnosis either, lol.
I know there are other instructors that are very straightforward, fact-based, and physical, but I'm not willing to devote the time to shop around much more. I might try other DVDs at some point (Jillian Michaels is supposed to be coming out with a yoga DVD!) but that's about it.