Yes James, I have some experience with the mpe-65 mm.
After going through all different kind off macro stuff for some years, I finally tried the mpe-65. And to my surprise I found it very manageable. I prefer the mpe-65 over a 100mm lens + extension tubes. With some good technique, it is for sure 'handholdable'.
Rent one and try it out !!
Hereby some pictures taken with the mpe-65.
magnification 1x
magnification 3x: