Lots of fun, but not a lot of replayability.
Being relatively new to buying Xbox live titles (I have Doom, Monkey Island, and Undertow), I wasn't too sure what to expect. After reading all of the praise that this game received and being a fan of Epic Games, I bought this game. Wise move.
Although the story is a little short compared to a full retail game, it is pretty good. You roam around the complex exploring and finding items. The voice work for the main character is the same guy that did Nathan Drake from Uncharted. Good stuff. I watched all the cut scenes and enjoyed the story through the first play through, but skipped most of them on the following play throughs. The achievements list kept me playing for a while. The game plays really smooth for the most part. Sometimes the aiming is clunky, but it only becomes an issue on insane difficulty. The graphics are beautiful and the level design is cool. It has a good balance of good easy fun and challenging puzzles. I played through the game 4 times. It was fun on each play through, but I think I'm done with it now for a while.
Considering Shadow Complex as a $15 Xbox Live Arcade game it gets a 9/10 from me. I highly recommend it.