Sampler is a fantastic tool for pseudo-granular synthesis. By moving the loop start in real time it's easy to create incredible motion in the playback sound. Unfortunately, loop start can only be automated through midi modulation - I usually use 'mod wheel'.
It would be fantastic if the loop start parameter itself could be directly automated through Live!
For that matter, why not add more automated parameters from the sample parameter page (sample start, end, etc..)