[King of Snake]

well the main thing you have to keep in mind if you're mixing in Live it to set the warp mode for the tracks to either Complex or Repitch.
Repitch is best since it doesn't degrade the quality or introduce any artifacts, but it works just a like a record player so if you speed a tune up or slow it done too much from it's original tempo it will sound pitched too low or too high.
Complex mode will keep the pitch as it was in the original regardless of what the tempo is, but it does tend to make the sound a bit soft and "digital" although it shouldn't introduce any real glitchy artifacts like you might get at the other modes (beats or tones)