I've been using the M1A for just under two years now and always get compliments on my acoustic tone. As much as I'd like to say it's all from my fingers, I think the pickup has a lot to do with it.
I find it to be bright and articulate without sounding too harsh. The notes are clear and have character owing to Bagg's floating coil design picking up vibrations from the soundboard and the body of the guitar, as well as the strings.
The cream colour of the pickup looks great as well. A minor detail but, one worth mentioning I feel.
The only thing that may be an issue for some people is the lack of EQ control on the pickup but as I tend to EQ from the desk or a plug-in anyway, I've never found this to be a problem.
Installation required some drilling in order to widen the strap hole and accommodate the endpin jack. If you're careful and have some experience with woodwork/read instructions online, this can be done at home, although if you have any doubts perhaps take it to a guitar shop or luthier.
Overall I would highly recommend this pickup, not too difficult to install, easy to use and it sounds great.