DPReview has completed their indepth review of the new L macro. I haven’t had the chance to play around with one yet.
“Overall, then, the EF 100mm F2.8 L IS USM Macro is an easy recommendation if you’re looking for exceptional image quality regardless of price. However potential buyers do need to appreciate that the increased cost over its older stablemate appears to pay mainly for the Hybrid IS system, which despite its clever technology isn’t hugely useful for actual close-distance macro work. Of course it’s still a great benefit for general-purpose shooting, which mustn’t be underestimated, and the new Hybrid technology appears to be a step in the right direction; but the marriage between macro and stabilization remains an uneasy one.”