I've had a camera with live view for over 2 years (first with the Canon 40D and then with the 50D) and I've only used that feature a handful of times. Only when tripod mounted and only to check critical focusing and reduce vibration in place of locking up the mirror.

It is heavily dependent on one's style of shooting and subject matter. I shoot primarily highly dynamic subjects in non-studio settings and there is no faster/better way to do it than having the camera plastered against my face - even if the camera is on a tripod or monopod.

It is ironic then that every P&S digital camera that I've ever owned, I never used the optical viewfinder with those. Go figure