It is very good !!! It totally killed my amp GAS, period. I have no GAS to get amps at all since I got it. Unlike guitars and pedals, both of which I can't seem to stop. The Atma does everything I want from an amp. It stacks well with OD pedals in its clean channel, or take a Klone into the crunch with a bit of break up fantastic. It has a very (I hate this word) transparent FX loop. It is loud, very loud if you want at 18W, don't think it is not because it is 18, it is ridiculous. Someone at another forum gigged with his to 100 people using the 5W mode and it kills.
My favourite mode is the 70's mode, in vintage setting.