Originally Posted by EarlyMon
When the Dalvik is clear, it updates at boot up.
According to the Android Police article, ART works the same way; they warned that boot up could take some ten minutes to compile your existing apps.
Thereafter, apps are compiled when installed, just as the Dalvik cache is updated when apps are installed.
Based on that, a factory data reset ought not be required.
I've been running it for 2 days; no issues so far. Correct, factory reset is not required. It just needs to reboot. It goes through its "Android is updating" routine. From reboot, to up and running, it took 8 minutes.