Only thing i've figured out to do with RC for haku is mixup, but that's generally only worth pursuing if you get a strong yomi, and its only worth practicing once you've run out of other things to practice.
It's also nice for saving your ass sometimes. Example: in one match, i landed an airdash>j.C way early against Tager, and i was like, oh gosh im gonna eat a tager buster, so i RC'd and used another falling.C to put more space between us, landed then did 6C>Shippu and won the round. In retrospect, RC was actually not the only option to save me there, i probably could have just poked him, but it was a safe option and it worked out well.
But in terms of combos i haven't seen anything that makes the stars worth RC'ing rather than just using a special cancel.