Yes, on my 3rd try. The first time I took a bad line to the left, and ended up in some slick leaves, back wheel slipped so I aborted early. The second time I was maybe 2/3rds of the way up when I hit a cobble wrong and it threw me off balance; I managed to unclip in time (I was on SPDs). The 3rd time I got it right. The rental bike had 34-front/36-rear gearing; clearly they knew their clientele and terrain.
Canton is short, but the next one I did (Boustead) was a real lung buster as it was quite a bit longer. When I was approaching the steep part a young local kid (clearly having witnessed a lot of attempts) yelled out "You're not going to make it!" I took some pride in getting up without stopping, although I was definitely gasping for air at the top.
That's good stuff, thanks! That would make for a fun hobby, to seek out the toughest climbs in the country and give them a try.