My only gripe with the M10 is that the panning base is never really completely locked. When using a long lens, any bump against it will cause the ballhead to rotate, although the panning knob is fully tightened.
This was not really noticeable until I mounted my 300 2.8 IS lens, although you have to be quick while mounting the ballhead to the tripod to get enough momentum with the twist so the ballhead tightens to the tripod. If you lose the momentum, the panning base will rotate before the ballhead is tight enough on the tripod.
According to Markins, this is the design limitation (although they don't really consider it a limitation). Panning base lock on the Markins is actually a steel rod that extends against the ballhead's inner wall, so the point of contact is very small, thus offering only limited locking capacity. My RRS BH-55, which uses a "drum brake" design is dead solid when locked (the panning base, that is).
Otherwise the ballhead is simply great. Fit and finish are excellent and operation is silky smooth.