I finished a Flixel iOS game last year. (made it for a client)
江頭2:50の 42.195km ～流石の俺も四苦八苦～https://itunes.apple.com/jp/app/jiang-tou2-50no-42.195km-liu/id545868250?mt=8&ign-mpt=uo%3D4
It uses Game Center, and also retina graphics for retina displays. Nothing very complicated, but it was my first game in like forever.
Maybe the coolest thing was the map editor, which was another binary/app really made for iPad. In our team, we used the iPad to make the level - the levels themselves synced automatically to the iPhone game app through iCloud. At the time of release, I just removed all of the iCloud code from the game. :-P It had a really WYSIWYG touch interface and at least I loved it. But had to kill it. :-P The game was released for the Japanese market, not sure now if it's available outside Japan App store or not.