I've used thrash, and it's a fairly good system. It places you very firmly in the driver's seat, and runs things on a blow by blow basis. Thus, in that, it's very detailed, but can also get tedius.
The system shares a lot of the strengths, weaknesses, and quirks as the GURPS game. It's flexable, but not balanced, can add things, but takes a lot of DM fiat to make it fun.
Character generation can take a long, long time. For us, it was about three hours of GM time per person, then one game to see how the character ran, and tweak them to fit the main idea a litle better. On the other hand, we ended up with The Iron Fist of Justice, who could soak almost as well as the Hulk (Bullets? HAH!); the Falling Star, the dodgey bastard with his namesake move of airial death; and lastly our 'pacifist' who used a dodge/chi-push combination to pretty amazing effect. The thing about building characters is that there's a whole lot of options, and not a whole lot of guide.
The moves aren't even close to balanced. Not at all. A light punch takes 2 ap, does 1D4 +str mod damage, has a +2 to hit and is a basic manuver. A heymaker takes 10 ap, does 2D4 + str mod damage, has a -2 to hit and will cost you a character creation point have. Chi-charge is aonther one that's just a great modifier to a move. For relatively low costs, it makes moves much more effective. The most effective guy I ever threw at the party had a combo attack (yet another easily abusable thing) that consisted of tons of light punches. The game is not meant for playing with Min-maxers, and not everyone will be equal. The book has it right in that aspect. The best way to build a character is to see what the character is like in your head, then find the moves you need.
The combat system makes sense until you try to run it. From there it breaks down. Simple things like "Can I choose to wait?", "What do I do with my leftvoer AP's" and such plague the system. I came up with a few solutions I liked, but there was a WHOLE lot of book keeping.
The system's rough, it's slow, it's easily abusable, and it requires a whole lot of work from the DM. But it's all worth it. There are just those awesome moments when you go into intense exchanges with your opponent, neither able to gain the upper hand, just to lure them into your signature super, and everyone at the table breaks out into cheering.
Oh yeah. It's awesome fun. Just expect to be playing all night.
