I saw one (two?) people complaining about instability - but they gone away. Maybe a lemon?
I was complaining about stability of hAP ac² (also ARM based). The problem was freezing of all wired ports (I don't really use wireless on that unit so I don't know if wireless froze as well) and had to configure watchdog for it to automatically recover. I've since changed configuration (went from
/interface ethernet switch based VLAN setup to
/interface bridge based setup) and I'm running beta versions of ROS.
It runs stable now, not sure which change did the trick (possibly the move towards bridge vlan-filtering as switch chip has at least one known bug regarding VLANs). Which also hints that problems with ARM devices are actually problems with peripheral devices (switch chips, wireless adapters) rather than CPU platform itself.
Hence if MT introduced high-end router based on ARM platform and wouldn't save dimes on peripheral hardware, it might prove as a stable and potent device.