I did it for 90 days and I hated it. Not because it was hard (it's hard in the beginning but you do see results quickly) but because Tony Horton needs to be shot. Most annoying person on the planet, bar none.
If you can stand his incessant yammering, you will do fine. Just eat primally (as primalfamily said) and you will see amazing results. 80-90% of you look is what you eat. Exercising augments this process and can even speed the process, but don't expect to exercise a lot and be lackadaisical about the diet and get the results you are after. Diet first and THEN figure out what exercise regimen works best for you.
People too weak to follow their own dreams will always try to discourage others.