If you play a lot of multiplayer games on your iPhone or iPad and have a Game Center account, you can easily create matches and play against your friends. Game Center is also great for tracking achievements inside a game as well as leaderboard standings between you and your friends.
I have to admit, I am not much of a Sudoku player. Not because I don't like it, but because I am horrendously slow at it and I always feel inadequate playing since my wife is about twice as fast as me solving puzzles on even a much higher difficulty. However, I sucked up my gumption and thought I would give Finger Arts latest release a try.