I've stayed away from any kind of backing tracks so far. The way I see it is it detracts from your creativity. You're stuck to that "track." You can manipulate it to a degree, but you're still "stuck to that track."

When I'm playing I never know what I'm going to do next. I play it as I feel it ("to a degree"),play the first 8 bars over and over (though I wouldn't suggest that), compose a new spontaneous ending, come in and go out when I want, mix up the songs...do a medley. Can't do anything fresh if you're busy following the backing track.

The same holds true for pitch-change gizmos (you should be able to change keys yourself), and pitch-correction machines (you should be able to sing on key well enough not to depend on "the machines."

But that all comes down to: do you want to entertain an audience or do you want to get better. Another way of saying "do you want to earn a paycheck or live in mediocrity for the rest of your career?" There's something to be said for both schools of thought.