Like I said earlier in this thread, I am on my fourth copy and finally got a reasonably good one.
Canon has lost my confidence with this lens. Reading peoples' troubles and experiences with this extremely expensive piece of equipment has left such a spurt taste. My own experience with Canon Canada with regards to a repair on my first copy was enough to make me look at competitor brand glass more seriously, even if the image quality isn't quite up to par. At least most of the competitors are offering 5x the warranty for half the cost.
Same here. I spoke to their service center "tech" and they were absolutely clueless.