Edit: After the new update to improve the controls I really have no complaints about this game at all. Game Center would be nice, but its hardly worth noting, and a real nitpick to bring up as far as Im concerned. This is my favorite iOS platformer among strong competition! Great work devs, thanks for listening to customer feedback!
My original review:
I get what people are saying about the buttons--it could be nice to have the sensitivity area extend past the visual button spots...but if you experiment with the button placements and put them in spots that are easier for you to get to, then it becomes almost a non-issue. But its worth noting that it could be improved slightly by increasing the sensitivity area or allowing users to increase the size of the buttons visually as well, as with Zenonia 2, for example.
This aside, the game could use an update with multi-tasking, and perhaps some Game Center achievements would be nice. But I still think that Giana Sisters deserves a 5-star rating. Its probably the best Mario-style platformer for iOS. It certainly is my favorite, along with Bounce On 2 (cant choose one over the other).
What this game has, is a great visual style that feels retro and also fresh and polished at the same time, great music as well. Wonderful gameplay, and strong level design are featured as well. If youre looking for something close to that great Super Mario Bros. feel with tons of polish and great gameplay, this is it. Well worth $5.