I'm getting it too!
Here's mine:
reboot ~ Mon Nov 3 10:05
reboot ~ Sun Nov 2 21:32
reboot ~ Sat Nov 1 12:36
reboot ~ Sat Nov 1 11:51
reboot ~ Thu Oct 30 21:48
reboot ~ Thu Oct 30 21:35
reboot ~ Wed Oct 29 14:48
reboot ~ Wed Oct 29 11:24
reboot ~ Tue Oct 28 23:27
Looking in the diagnostic reports:
One was notifyd which I guess is from the notifications produced in notification center - I did see the system hang after displaying a notification and it looks like it's done that a bunch of times. I've tried disabling all my possible notifications but some still sneak thru.
Looks like Coregraphics Windowserver crashes for a number of reasons. I can't really determine why.
I also see something called Spindump that has crashed a couple times too.
MDS too but I believe I know a reason for that. I have a number of external drives but they're not always on so if MDS was trying to index an external drive while I was trying to shut it down it might not have been too happy about that.
Looks like Yosemite has a bit of polish needed.