I like the system. I do not feel it is overpowered, either. I like the ease of multi-classing, and the goodness that can come with others taking the feats to get some martial manuevers.
One of the biggest concerns that many have are the warblade's seeming replacement of the fighter. I think that it very well can replace the fighter, if you want. I don't think I'll be doing that, as I think the fighter is best relegated to the role it suits, a dip class.
Others don't like the supernatural type manuevers. I think they fit in d&d very nicely. The swordsage for instance can be an elven sword-monk, or (as I will soon play,) a psychic warrior. It depends on what flavor you wanna use.
I think you could also do some cool things by just using the manuevers and not the classes, as Spunky is doing. It could give some cool boosts to the melee classes.