[Brightcolours]

From memory, but I might be wrong, the Canon 100L macro doesn't accept teleconverters which protrude into the lens. Some Kenko ones don't, so those would be ok.


As for the IS, I'm not up to date on who does IS like the 100L, which compensates for both tilt and shift. Normal IS only compensates for tilt, but shift can get more important for macro. It still doesn't correct for movement forwards/backwards nor rotation. I haven't used it myself so can't comment on its relative effectiveness.

The Canon 7D (and 7D II) has a feature called "Intelligent Macro Tracking". When you put a macro lens with USM on the camera, like the 100mm f2.8 L IS USM, and set the camera to AI-Servo, it doubles the AF scan frequency when used at 1:3 and bigger.

This then acts as back/forward movement correction. Of course, a TC may mess this up. I do not know which other cameras, since the 7D introduction, have this feature. It is not widely advertised.

 

No Kenko TC protrudes (the Canon and Sigma converters do protrude), and you can put them on every EOS mount lens. Not on EF-S lenses, as they have protruding backsides.