General

If you're someone who's worked out less than 4 days a week, 1.5 hours a day, or if you're new to working out, I highly doubt you'll be able to last a week without either finding a shortcut or quitting altogether. I'd say good luck, but it's not about luck.

Heard a lot of good things about it, a lot of people say it's "insane". No personal opinion, though, never tried it.
~No cardio crew~

edit: I should mention that even though it has had positive reviews, it is by no means an optimal routine. The components that make it successful are simply commercially-driven, in that it's a home workout, it includes different movements to keep you engaged, etc. These elements make it good for the general population, so I'm not gonna knock it; better than wanting to do hill sprints and HIIT only to sit on the couch and lose motivation because it's exhausting and boring.

Generally those workout things work as long as you follow the routine. If not, well either something's wrong with your body, or you're not doing it as described.

i think my forearms size increased