Saw it myself, since i'd seen the other two, but thought it was one of the word films I'v watched in a while (not a patch on the new x men!). Some of the 3D was cool, and there was enough fighting in the last hour for it to become watchable (though how many times they jumped through glass and not one of them got a scratchh, ), but the film was 2 and a half hours long, and the first 90 minutes bored me to death. Script and acting awful all round. I came to the conclusion that it would have been a much better film with just CGI robots, without any of the human actors.
On par with number two I'd say. If you liked that, I'd reccomend the first film, that one was genuinely good (I thought)!