Although the story is not entirely original, the application of the premise and incredible visuals compensate for any lack of originality in the script. If possible, watch in Imax 3D, to fully take advantage of the visuals.
All acting was decent or better (the colonel was well played, as was Sully - look forward to him in Clash of the Titans).
Probably the best movie I've seen this year (or tied with Watchmen).