Gears: it's a ball roller with dynamic levels and eye-catching graphics. That's about all there is to it... and that's not necessarily a bad thing. The ball rolling genre is all about discipline and control; it's meant to be simple.
The game differentiates itself somewhat from others in the genre in that you can choose between tilt or swipe controls. It's an unusual option given how well suited tilt controls are to ball rolling, but the option to touch and drag instead of twisting your device all over the place makes Gears a better casual game than its competitors.
We had no issues in testing on the new iPad and an iPhone 4S, but word on the street is the game tends to hiccup on older devices. Hopefully this will get cured in a future update.