Way too long, IMHO. I doubt this will be the "blockbuster" to challenge "Titanic" as some were speculating. The special effects were cool, and the fight between 3 Rexs and Kong was cool, though unrealistic as Rexs are solitary hunters and would have turned on each other as well. He also seemed to get glancing blows when his body got bitten, no way! Large chunks of flesh would have been ripped off, but hey, we cannot kill Kong off too soon.
Good cast, good fun, but all in all 3 hours was too much, IMO. Worth the money on a matinee if you want a cool movie to watch.
Jackson did a good job, but there is only so much you can do with a movie like a remake of King Kong.