Soundtrack gets repetitive, strategy is non-existent, and once you get the Achievement points, there's really no need to come back.
UNO is quite possibly the finest of Xbox Live's Arcade offerings, or at least the one offering the most bang for your buck. It achieves pick up and play perfection, as there's always someone on and it will take you seconds to join a game most of the time. Player matches allow you to tweak your options to your liking and match up with your friends rather quickly. The game functions with little lag most of the time, and the inclusion of Xbox Vision support so you can mock your opponents after stiffing them with a Wild Draw Four three times in a row by doing a victory dance in your Spiderman Underoos is fantastic for you, not fantastic for the poor bastards who have to witness it.
The game plays simply, even if you don't know how to play UNO when you download the game it will come quickly to you (unless, of course, you're a *bleep*, in which case let us know and Tommy will come back and hit you on the head with a tackhammer). The game automatically highlights the cards in your hand you can possibly play on your turn, and actually playing the card is as easy as shifting the analog stick left and right to select your card and pressing "A" to play it in the middle. The all important "UNO!" call (which sounds in-game like it's being spoken by a chorus of Spanish Munchkins) is activated with a press of "X" upon the turn when you can play the second-to-last card in your hand, and if by some reason the idiot to the left of you forgets, you can use the challenge button ("Y") to stick him with two cards for forgetting. The game will prompt you to pronounce UNO in the lower right hand corner, which is good, because it's likely you'll forget the first couple of times and then curse loudly into your mic, which might anger the creepy forty-year old to your left watching the sixteen-year old girl with her vision cam on your right making pouty faces. I hate pouty faces.
The only problems with this game is the inability for more than one person to play on one console (obviously this was included because of the potential to cheat online, but is it to much to ask that you keep Player 2's cards hidden while Player 1 plays, and vice versa?), the instrumental soundtrack gets tiresome quickly (you can alleviate this by streaming your own music onto your console, though), and the relative lack of depth--much like the actual card game, UNO is fun only until you get tired of playing cards in the middle of the pile, which will happen quickly if you've got Halo 3 or Bioshock sitting next to your console.
UNO is a simple, addictive, bargain-cheap Xbox live game, and should be downloaded by everyone for those brief few moments of free time you have to enjoy something on your 360 between everyday activities.