I've been running it since day 1, and have performed at 2 corporate gigs with 16 hours of Modul8 open and running - no crashes or slowdowns.
Only quirk was Madmapper crashed once over the course of the two days. This is on a rMBP.
No Kernel Panics or weirdness in general usage either. That said, unless theres something you need/want in 10.10 and 10.9 is working fine I wouldn't rush.
@Deanbob - by 'sort out' 7 Macs running 10.10 what do you mean? I've had no problems with stability.