Engadget got a sneak peak at the game, and while it noted the gameplay was fine, it did mention the graphics and lighting were cut down 'dramatically' and the experience was 'subpar' compared to its console versions.
In-game lighting and shadows are cut down pretty dramatically, as are art assets. The grandeur of Rapture is distinctly less grand, which sucks some of the life out of one of my personal favorites. The first thing you'll notice is "iOS fire." The game's opening -- a plane crash -- puts main character Jack in the ocean surrounded by some hideously ugly fire animations. It's the first hint that the iOS version of Rapture has been shrunken down to fit within Apple's app store file size limitation, and it's a nagging issue that I couldn't shake in my hands-on time.
The game will have touch-controls on the screen, which is not ideal, however you can play BioShock on iOS with a gamepad. It will arrive later this summer for iPad Air, iPad Mini 2, iPad 4, iPhone 5S, iPhone 5C or iPhone 5 at an unknown 'premium' price.