Full Disclosure: I am a long-distance friend of the Peryton Publishing crowd. While I may have a little personal bias, my correspondence with Tom developed originally from my playing this game at Gen Con (2009) and enjoying it, so I think I can still offer a fair review.
WHAP's mechanics are based mostly on primary attributes that you roll randomly and "inherent skills" derived from combinations of the primary attributes. The core mechanic is to roll against a target number by adding one of these attributes or inherent skills to a pair of dice (six sided - this is all six-siders). There are also perks, secondary skills, "and whatnot" mentioned to flesh out the character, but not much is said about this beyond a page of instructions and one example. The concept is explained clearly enough, but I'd like to see a little more detail for guidance. The business of cobbling together the inherent skills seemed strange to me at first, having never played a game that does this, but in actual play the math is already done and the derived stats make everything relevant in a fun, unobtrusive way.
The game is full of little touches that you might not notice until you start playing it. For example, you might see that a weapon has a 3d+2d damage rating. Why not just say 5d? Because the ASTRO rule lets you keep going if you roll all the same. This gives you a situation where some weapons usually do a fairly typical amount of damage, but then have an increased potential to be surprisingly deadly. The authors would probably have done well to toot their own horn on things like this, but I guess if it works at the table that's all you need.
WHAP loses one star because, like I said, there are spots where it could use more hand-holding and cheerleading to get new readers excited about the rules. It's still a very nice package with good rules and a lot of pulpy attitude and I can tell you from experience both as a player and later as a GM that, in actual play, it delivers.