A little surprised not to have noticed Atma-Spheres on this thread. Compared to the other amps I have owned, tube or solid-state, the MA-2's have outperformed all in nearly every category. Bottom slam, midrange transparency, and extension up top...all beautiful and musical. This, of course, is with the system I have assembled. Avalon Eidelon, Jadis preamp, CEC/ Audio Note digital, Clearaudio TT, FIM cable. I have enjoyed many systems, but none for as long or as consistently as that which I have forementioned.
Reliability has so far been a non-issue. The 220 watts/ channel offers more than enough juice. The heat generated is something else. My room must increase a good 8-10 degrees. Great in winter, but summer....
I have not compared to other OTL's but reports on performance carries similar subjective remarks. A cleansing in clarity, bringing the listening experience closer to the recording venue. Must be heard in a well designed system.