"I mean, Insanity has breaks... you can just make it "harder" by not having breaks. Or doing the exact same thing for longer than the DVD runs for."
^This defeats some of the purpose, which is to have more of a HIIT-like workout. You go extreme for a few minutes, then rest for 30 seconds before going extreme again. In terms of calorie burning (and yes, ramping up your metabolism) that's technically the most effective workout style.
My husband and I both did Insanity and loved it. He's done it 3 times now and I've done it twice, although it is my default winter workout to choose a video to do 3-5 times/wk. Doing it with another person really helped us stay motivated, especially since he enjoyed the workouts I hated and vice versa. I've had knee problems in the past and it started to bother me a bit toward the end of month 2 but not too badly. Have you checked your form? I hate to say it, but that can cause a lot of problems.
The one injury I got, the first time through, was that I tore the fascia in both shins. I had to modify a couple of the stretches the 2nd time through but that solved the problem.
And as a woman, I felt that it built a lot of strength in me, particularly in my arms which tend to be weak and a bit flabby. I could barely do 10 "girly" pushups when I started the 1st time and by the end I was almost keeping up with the videos. I didn't lose weight, per se, (nor did I gain) but I lost a lot of fat and gained muscle instead. Clothes which had been on the tight side when I started were on the loose side when I ended and the husband said he noticed a huge change in me.
That being said, I do understand that workouts often need to be tailored to individuals. I think the bad reviews on here are simply because this workout style doesn't help every body type. So if it's not working well for you, experiment with other workouts and try to find one more suited to your body type.
