dear mouse:
in spite of the fact that aural training is essential, i'm not talking about that. the danger of this practice (the same of metronome practice, btw) is to remove your brain from the task of controlling what you are doing, and let your hand alone, so to speak.
the point is: when you don't have any external support, you must know what is happening when you play, and thus focus to control speed, and so on. if you have a back track, and you play in the correct speed and volume, it's very easy to do it without any concentration, what can be destructive to your ears (and to your technique as well).
perhaps, the real question is: what are you looking for when you rehearse? if the answer is not "the musical result", something is very wrong, imho. then, the use i have to that kind of help: metronome to control speed development or to help keep the beat, back track to solve a particular musical problem. the danger come when you use your back track, and your goal turns into accompany your back track...
just a final word about recording: essential.
best!