I have a Rega P6 with a Hana ML mc cart and I use a Michell Engineering clamp (the Rega-specific version, which is made for the correct spindle height). It's lightweight, made of low-resonance Delrin, and uses the twist/collet-type clamping method.
To me, music sounds tighter and more precise, with better soundstaging and crisper transients (although I know how subject many of us are to hearing what we want to hear...)
I can't see how the clamp would stress the spindle bearing, as it only compresses the record to the mat, platter, and subplatter, all of which ride on top of the bearing.