I've soon had it running on my phone for 24 hours, with no rebooting or any other serious issues. There are bugs and unfinished stuff here and there, yeah, but if you don't mind that too much this seems totally usable as a daily driver so far.
I hope it stays that way for me, because I really don't feel like going back to KK now. Even though a lot is unfinished, what's there makes the experience so much smoother and more pleasant than before. KK feels old and stale once you've gotten a taste of L.
Did you do a full wipe or just install over KK and keep all your apps/data?