I've found if you set Kicks up to log on and off every so often (which you really should do anyway), it loads up the most appropriate profile and levels quicker. Otherwise it seems to stick with one zone until it completes all the quests.
There a couple of little hickups, especially if you get some bad interactions from the opposite faction.
I had some questgivers in Thrallmar get killed a few times and one of my bots was stuck there trying to hand in quests which weren't in the questlog. I just manually played for 10 minutes and it sorted itself out.
Mists content worked flawlessly for 5 characters with one minor exception in Kun Lai, where a mini-boss had some adds which needed to be killed prior to killing him, and my warrior char got stuck there.