Price paid is £299 sterling, not dollars, but site won't accept £
I've had this lens for about 6 months now.
It's superbly sharp at any aperture, peaking somewhere around f2.8~f4 but still excellent at f2.0. Currently I'm using it on a crop camera so I can't comment on FF corner sharpness. On a crop in astro-photos, the stars in the corners are good at f2.0 and excellent at f2.8 (very rare performance), in my experience DPP lens corrections are only noticeable at 200% view.. and then only if you look closely.
Most people would compare this with the 85f1.8. In my opinion this wins by a small but significant margin. Check out the DxOmark data for the 85 vs 100 and you'll notice just how soft the 85 is wide open compared to the 100, the 100 at f2.0 is probably equal to the 85 at f2.2 or 2.5.
This lens doesn't have IS, but that would cost more and would mean there's more to go wrong. It does have proper USM focus, so it's fast silent and should last with no little plastic cogs to break on you. Neither front nor rear element move at all, so dust ingress is going to be a slow process and filters don't spin round as you focus. The materials are a mix of metal and high quality plastic, with metal filter thread and metal mount.
Canon do not provide a free hood, but a quick check on ebay and you can get one very cheaply, I paid £3 for mine.