I've been on 2.2.12 since it came out, and have found it to be very reliable. There are only 2 minor issues I've seen... 1) Station broadcast signal dropouts seem to cause Tablo to reboot, and 2) When watching live TV, if I have recordings scheduled (not sure how many it takes) Tablo will kick me out of live TV back to the program guide when the recordings start. I'm not exceeding the number of tuners I have, so I suspect a s/w bug. Using a Roku to watch, and it seems pretty repeatable. Haven't tried with my Nexus Player.
Also, yesterday had a circuit breaker kick off. When I switched it back on, everything came up but could not connect to Tablo. A quick reboot brought it back online. Not too concerned about this one, as that breaker rarely kicks off, generally when a portable heater or vacuum cleaner are plugged in.