The biggest problem with the W&G control scheme, for me, is that it destroys immersion and uses some obscure control combinations - shift, mousewheel, etc. - weird!
It's gone from a PC suitable interface - mouse for S&M - to a console-hacked compromise (probably to suit it to the Wii control stick).
But here's the real killer for me - it has a tendency to bugger up the animation. If you walk Gromit (or Wallace for that matter) into a wall in W&G, the walk cycle looks painfully computer generated and stilted - he goes from being a character who could genuinely exist in the world he's in, to a computer-driven pawn moving in a stilted fashion against a series of invisible barriers. Also, the jilted transitions that force movement in one of eight directions (as the PC doesn't have analogue control from WASD) only exacerbate the problem.
I don't see why, when the mouse control worked well in S&M, we seem to be going backwards here - affecting animation and immersion - just to cater for the console tards...