I grudgingly will offer you my observations. I have had the chance to listen to one. They are one stout amplifier after the mods and it seems as if it is effectively doubled in power. You can just keep turning it up and up and up without fear of normal clipping distortion way beyond where you would normally have to stop. The mods do not seem to affect the sound signature of the amp, just the available power. While I can't stand the man who does these mods, I can't really balk about what he does to them. He does do a really good job. Keep in mind, these are used amplifiers that he performs mods on so be sure to ask about the cosmetic condition of the exact one you would be interested in as it will not look new.
That said, it has been said by Rolland and by Bob himself that what mods are done do tax the transformer beyond what it was designed to do and that there are no replacement xnsfrmrs available. So, basically when the xnsfrmr goes, you would have a nice, heavy Carver door stop.
Now, a bit of advice from me. I wouldn't get the M1.0t MKII unless you have a system that's laid back on the top end and needs plenty of bass and lower registers. Get the M500-t MKII. It has the most preferred overall sound signature of the non-esoteric or rare Carver amplifiers. This is not only my opinion [concerning the M500-t] but the opinion of forum members collected over a couple of years. It wasn't unanimous but it definitely leaned more to the M500-t than any other Carver amplifier, by quite a bit.
In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence.