I bought the M10 after reading about the Markins heads on Nikonians. It took some work to convince myself to spend 350 on a head but I didn't want to slack. I've wasted too much on crap equipment and now I try to get the right product the first time.
As far as use goes, it's a pleasure to use. Once I set the tension to the "sweet spot" for the rig I'm using there is no need to lock it down or loosen it to recompose. I have not used any other of the top tier ballheads (kirk, RRS, ArcaSwiss) but cannot imagine them being any better than the Markins.