I am currently doing Insanity for the second time. The first time I did lose some inches but I felt that I really was more conditioning my body to be able to go longer and workout harder rather than lose inches. I did not follow the diet plan with the first time so I know that also didnt help but now that I am for the second time the results are great.
I have tried P90X but a lot of the moves I had to just stand there and wait till it was done because I just wasnt in shape to do them. I find Insanity to have moves that can at least be tried.