Acting was great, plot was average, execution ... not great. Tom Hardy was fantastic as the villain Shinzon, as was Ron Perlman and all of the original cast. All did an excellent job. The plot revolves around Shinzon (who is a young clone of Picard or something) who has now taken over the Romulan Empire (I think). Picard and crew meet Shinzon and he seems a little bit insane. They discover that Shinzon is dying and needs Picards blood (I assumed). Eventually Shinzon abducts Picard and B-4 (Data's inferior brother, who they had found on a nearby planet ... sort of like Clint Howard). Picard escapes with the help of B-4 (who is actually Data, pretending to be B-4). Back on the Enterprise they confront Shinzon in a ship to ship battle, eventually ramming his ship with the Enterprise. Picard makes his way to Shinzon and stabs him, meanwhile Data dies while destroying the enemy ship.
Back on Enterprise, everyone is sad because Data is dead. Picard eventually realizes that Data transferred his program into B-4. Eventually they will be one in the same. Most people did not enjoy this movie. It certainly was not terrible, just incredibly average. When it becomes obvious that Shinzon and Picard are connected in some way, I was waiting for Shinzon to say that he was Picard's son. Like at some point during TNG Picard knocked-up some random alien woman. That would be more believable.