Are you extremly pleased with the EF 8-15?
I'm not sure how to quantify "extremely pleased". For my purposes? Yes. But I am an amateur/prosumer that shot film and manual focus longer than I've been shooting digital. And this is a specialty lens that gets limited use on my 6D and 1DX2. My initial impressions with it on the R6 are more about the R6. I have more options to consider about the best way to get the image I desire, particularly with AF since I often used MF in the past.
The lens operates just fine. I've never had any complaints with it over the 9 years I've owned it on FF or APS-C bodies. It even spent time on my M series before I picked up the manual focus Samyang 8MM f/2.8 Fisheye for the M. The 6D/EF 8-15 has been on the trail with me, but I like the smaller size of the M/Samyang for the trail. The EF 8-15 seems so small now compared to the EF 11-24.