Major Nelson is the Director of Programming for Xbox Live. If you want the latest information on what is going on at Xbox live follow him either on twitter.com/majornelson or his blog (Majornelson.com)
Today for instance, he posted information about a new Arcade game called Spare Parts. The price is 800 Microsoft points. However, you can click on a link directly from his blog to add the free trial to your download queue. How awesome is that.
I downloaded the trial of Spare Parts and instantly knew I was going to like it. It had story line, cute characters, and instructions. I was afraid with it being an arcade game it would be a start screen and then okay go. But no, it had an intro movie and a step by step tutorial. The game play is very simular to Sonic the Hedgehog. You collect coins, beet up bad guys, and find items. After about 15 min, the game asked me if I wanted to upgrade to the full version. I said yes, which I am glad I did because I had not realized that I was going to start from the begining again. I am glad that I had very little to redo.
The only frustration I had with the game is that you are limited in looking around. However, after a few minutes I got used to 2 dimmentional area.
All in all I would recommend Spare parts.