Upload & Sell: Off
I've sent 2 lenses in for service over the years, 1 was in warranty (70-200 IS II), 1 ended up not being covered by the warranty (100-400L). The 70-200 needed the IS replaced along with another lens element and was returned good as new without a problem (within a week). The 100-400 needed the zoom friction ring replaced along with the IS. That repair took about 3 weeks due to backordered parts. When I got the 100-400 back, it was better than before, smoother zoom, sharper image wide open, and more responsive IS.
I've had some other stuff done too, but it wasn't warranty work. Just some shutter replacements and cleanings and such. In all, I've been very happy with Canon from a service standpoint (and equipment too obviously ).