It is a very basic action film, and that is a compliment. It's an even simpler premise than Speed. It doesn't have an actual villain, they're just trying to stop a runaway train and that's it. If you've seen the trailer, you know the story!
In fact the weakest moments are when they try and add backstory to the characters, which is really not needed.
It's fast and furious stuff and if you like action movies, you'll like this. It's Tony Scott directing, so if you like the style of Enemy of the State, Crimson Tide, Man On Fire, etc, you can't go wrong. By the way, there are already two reviews on site from Marie and Dr. Hasslein...