I am looking forward to when we have fire and forget snapshotting system so that we all have rolling backups. I would also like the send snapshot features they have added recently for keeping multiple drives in sync (I currently use unison, but I think this could be faster/better).

Plus copy on write should be pretty cool (cp becomes as fast as mv), though I could see it allowing me to engage in some suboptimal behaviors of copying tons of stuff and counting on CoW to avoid actual duplication.