Perhaps don't try to go in the Iphone way, caus such control
is similar.Why not staying with keys ?
Right, Left, Space to Jump, C to shoot etc ...
And let the user redefine the keys if needed !

I'm not sure you will be precise with mouse, for platform style.
Caus platform works lot more with keys, more natural for that type of game. A good way, submit the two methods to players and ask them the better way, i think the majority will vote simple Keys ?

Well juts my opinion !