Portal 2 is a masterpiece and one of Valve's absolute best games.
Pros:
-Innovative gameplay
-Excellent new gameplay mechanics
-Terrific voice acting
-Imaginative story
-Great character development
-Ties up loose ends from the original Portal
-Good fun co-op
-Good graphics
- Puzzles aren't frustrating yet slightly challenging
-Steam works well
Cons:
-Could be longer
-Not hard enough
-Not much replayability.
-A little short
Portal 2 is a must buy. It simply is a magnificent game. At it's core it is just pure fun. Creative, challenging and cool. There are so many good things about Portal 2 that it is impossible to list them all. You'd get 15-20 hours of gameplay combined between single player and co-op. Each one has its own story and you don't have to play them in order. Co-op is shorter than single player.