I dunno man, I used to turn the pitch all the way up on my multitracker, in hopes of getting better high frequency response!
The thing is, tape is pretty cheap, so why not just record at the normal setting? Plus, if you record a multitrack tape, and then bring it to a friend's house to record some overdubs on his recorder, it'll end up being a big mess trying to get the pitch just right, unless he has the exact same recorder as you (and assuming the pitch knob is calibrated exactly the same).
Then again, if it's just you, and if your mics and stuff aren't so great to begin with, then I guess there's no real reason why you shouldn't try to get more bang for your buck.... Whatever works for you, right?
Ryan