The basic rules of Uno still apply: there's a discard pile, and four players take turns playing valid cards onto the discard pile with the hopes of running out of cards before the other players do. The catch with Uno Rush is that you have about five seconds to play your cards, and rather than actually selecting and playing a card, it's your job to properly sort your hand. When your turn comes around, if a playable card is at the front of your hand, it automatically plays. If the next card combos with that first card, it plays, and so on and so forth. So while the game frantically moves from person to person, you're trying to organize your hand to combo away as many cards as possible while also keeping on eye on the other players in order to guess what color or number will be on top of the pile when your turn comes around. It's hectic, and if you end up with a lot of cards in your hand, it starts to get overwhelming.
It'd probably be a little less hectic if you had better control over your hand. You're limited to just moving a cursor left or right along the bottom of your hand and moving one card at a time. There were plenty of cases when I wished I could jump to the front or back of my hand, or select a group of cards and move them all at once. That would make the hands much more manageable... which probably would defeat the purpose of the entire game, since the game always seems to hover at the edge of chaos.
The game's scoring and modes are more similar to the previous Xbox Live Arcade release of Uno. You can set up partner mode games, elimination matches, and vary a collection of rules to create your own set of rules. You can also enable the Xbox Live Vision camera, but with all the intensity of Uno Rush, the camera seems like it wouldn't be of much use. Instead of all the weird things you could find people doing during a leisurely game of Uno, Rush is more likely to give you images of people leaning forward, sweating over the order of their hand. Either way, I found it tough to find anyone with a camera going in the first place. Also, since you can see all of the other players' cards, you can play offline multiplayer in Uno Rush, something you couldn't do in regular Uno.
Ultimately, the length of time you spend with Uno Rush is pretty dependent on how cool you are under pressure. If the thought of a fast-paced multiplayer card game where you have to keep one eye on your cards and the other eye on three other hands excites you, chances are you'll have a great time.