I had lots of restarts during the first day, but after I took a factory reset on the device it seemed more stable. But I'm still have devices that have a connection but suddenly doesn't seem to get their dns lookups through.
At the moment I'm clearing nvram, do a power cycle each upgrade and after that I configure the router again without restoring settings...
I don't have problems with DNS although it sometimes takes a few minutes before IPv6 is actually working... I also disable the automatic lookup for DNS servers and set them by hand on WAN (IPv4) and IPv6