Well, since the Touché is so fast and sensitive (almost audio rate), you can add a level of subtle detail and percussive transients that few other controllers allow. Synth programming with it is like creating a virtual string or drum skinn, and then being able to physically tap, slap, strike, and slide your fingers over it. No need for envelopes or LFOs to do musically useful things.
One interesting technique is to use your thumb to transfer arm weight into it for big and slow motions, while using your fingers to add transients over that. Since there are two vertical sensors (front and back), it also matters where on the pad you place thumb and fingers.
I think the Touché is definitely worth having for its unique capabilities alone, if you’re into that sort of stuff, but it certainly a great high precision 4D controller for the usual modulation, expression, and bending as well.