Just to add to what has already been said about realism, last year I asked @timaeus222 about how to make my sequencing less mechanical. The context was instrument sequencing, but I think it can be applied to percussion too:
I have since found that sequencing percussion is actually pretty wide open in FLS; I can either play the percussion parts out through the plugin (under one channel) or pull the actual WAVs and manipulate each waveform directly (assigning each WAV to its own channel), depending on what sort of 'realism' I am looking for with the sound. Sometimes even slight EQ adjustments, slight pitch adjustments, or even where the drum skin is struck can effect the 'realness' of the sound; I, however, have had very little chance to experiment with this, so I can't advise much closer than that at this time.
I hope this helps ... and I totally endorse air-drumming as a timing and sequencing aide as well.