Animal Pak - Has an excellent profile, but for whatever reason a couple of those pills just didn't agree with, lots of stomach trouble. Also, you can't be squeamish about downin the pills cuz each pak has a shitload. I finished my canister but didn't get anymore because of the stomach issues, but that probably was just me. If it weren't for that I would have stuck with them.
M-Stak - Wasn't too impressed, noticed a lil better
intensity and better pumps than nothing, but you can get better of both with a pre-workout stim and an NO product. Not worth the money in my opinion.