Classic Technic was brilliant, but when they switched to 'studless Technic' it became far more difficult to build creatively with it (even if it enabled far more intricate builds with complex mechanisms, like the gearboxes in the supercar sets) - there was no natural 'up' direction any more, and building anything became more of a 3D logic puzzle than just building with bricks.

Real shame that they discontinued Mindstorms, though.