I am currently doing a TBT program with 3 sets of 30 reps per exercise. I HATE it. I went to a physiotherapist because my lower back was hurting and she suggested this. After I tried it once I was ready to drop it right away. The weight I have to use to actually make it to the end of the third set is embarassing (yeah I know, 'leave your ego at the door', but still..) and with 630 reps in total (7 exercises) this program just sucks the life out of me.
I stuck with it though just to see what would happen, how my body would respond, and because maybe, just maybe, the physiotherapist knew what she was doing. I still hate it but after 4 weeks I have learned a couple of things, the most important of which is that you can PUSH through the pain.
My workouts have always been a high weight/low rep kind of thing. I've never really had to deal with the lactic acid buildup you get while doing higher reps, and if my muscles did start to burn during a workout, more often than not I would not make it to the end of the set. Well, with 3 x 30 you can be sure you start to feel it burn halfway through the second set.
It took me a while to distinguish this physical discomfort from physical exhaustion, meaning I didn't immediately realize it can hurt like hell but I'd still be able to raise the weight. Now I can finish three sets without stopping for rest and I'm sure this new knowledge and experience is going to help me greatly when I go back to heavier weights.
I've learned a couple of other things as well, for instance that a high rep workout can do nice things for your physique, although most people will say you're not building muscle just endurance. While there are definitely better ways to build muscle than a 3 x 30 program, the mirror is giving me some good, positive feedback. Maybe I'm just getting more toned, or maybe there's real new muscle there, but I can definitely recommend trying a workout like this for a few weeks if only to shock your body into adaptation.
So what new knowledge and/or insights have you gained from one program or another you've tried?