I remember a while back finding information in the forums on this DIY amp was troublesome, as searching for "M^3" doesn't work and, as well, it's referred to as the "MMM" and "M3". So, without further ado, courtesy of a couple of other Head-fiers, here is a list of M^3 threads:
If you want further information, I think the following threads have some valuable subjective/objective information and comparisons/impressions of the M^3.
BTW, having compared a few different sets/combination of opamps, I have to say they make a significant difference in sound. I suggest you roll some to match your headphones. I've found the AD8610 (my current opamps) to be the most transparent (but not always the most pleasing).