You cannot change controllers mid-game, because your profile (and thus, your save game) is locked to a controller. If you use another controller, you'll need to sign your profile out of its original controller, which will cause the game to kick you back to the Press Start screen. There was really no way around this. = P
The up/down left/right deal isn't so rough, I found, once you get used to it.
Finally (and this is all in the "controls" submenu in Settings), while you may change fields with the orange fret, I find it much easier to use the alternate method, which is holding down all four primary frets at once and strumming. This way your fingers never need to move.
As for the drum thing, using the same button for field switching + casting spells wouldn't be good, I think. Every time you cast a spell you would automatically switch fields, which would be INCREDIBLY annoying. Plus you could only switch in one direction. = (
And finally, almost zero chance on PSN. Sony has not contacted me and they have a closed development environment. I'd have to pay thousands for a dev kit, and that's only if they accepted me as a registered developer, which is highly unlikely. = P
(But Steam, man!)
