Re: canon 100 macro
I haven't tried the new IS 100mm but I have been paying attention to (bits of some) reviews and seeing lots of pictures. Whether or not IS is any use will depend on the situation and subject but I expect it will be handy sometimes. It sounds like the IS 100mm has a smoother focus ring so even on a tripod it sounds like a nicer lens to use (the focus ring on the old 100mm is too highly geared and compared to other macro lenses I've used it can be fiddly when trying to focus accurately). I haven't noticed any pincushion distortion in beastie pics which, other than money, seems to be the price you pay for the IS version.
Go on, treat yourself
Would quite like one of the new ones myself
Andrew
A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. - Antoine de Saint-Exupéry