here's my two cents:
it was easy to get used to the controls, sometimes I felt a bit disoriented as Wallace moved in an unexpected direction, but it may be because I'm too used to playing shooters on the arrow keys. it's definitely worse when Wallace moves so far to the edge of the screen that he isn't visible - though it's a camera change issue in itself.
I am baffled by one thing, though. there are two scenes in the demo - one is the walking-around-adventuring type, and the other is hi-adrenaline action. now, you're direct controlling Wallace in the first scene, where point-and-click would be perfectly adequate, and there's no direct control for Gromit in the second, where it could amplify the heat of the action.
all in all, it seems to be a good control scheme, the players will need a bit of time to settle in it, and I also think there'll be much polishing going into it during the series.