If you still haven't hurled yourself into the maelstrom that is Geometry Wars 2, here's one last push to get you off the fence. PopMatters has posted my review of the game, and here's a snippet:
Geometry Wars 2 exhibits one principle of superior game design that dates back to the early arcade era and links to its spiritual predecessor, Robotron 2084. Great games ramp up their difficulty just enough to entice you to improve your skills, but not enough to permanently discourage you. This is a difficult balance to strike, but Geometry Wars 2 nails it perfectly. The game encourages you to keep trying, and this repetition is bound to make even weak players feel they are making progress. On the other hand, allowing a novice to observe an expert playing the game can result in one of two outcomes: a slack-jawed look of utter awe, or the novice screaming in terror and fleeing the room. This game eventually gets very, very hard.
You can read the full review here.