I've had mine for 2 years now, it makes up the short end of my EF 40f2.8, EF 100f2.0 and EF 300f4L IS trio, which on my crop body means I'm always shooting from a ways away. I guess that's just my personality, it suits me. The 40 on my 60D was what I took to NYC early this year and it suited me surprisingly well, despite a lot of crop body owners not warming to this FL, so YMMV. It is sharp and focuses well, it is almost as sharp and contrasty as the 300mm lens which is my standard with what I own.
There are a lot of great choices in this range, the 35f2 IS would be a better choice for me, or the pair of EF-S 24f2.8 STM with the EF 50f1.8 STM would be smarter and not terribly more expensive. At the time, I decided to try the 40mm lens when I was inspecting two years worth of use of the EF-S 18-200 zoom, and realized that 20% of my shots were zoomed all the way to 200mm and even then cropped, and the other 80% were all within the 24-100 mm range. My priority is dimly lit stage photos of my High School aged kids in candid photos where there is some subject movement, which limits my minimum shutter speed around 1/80th sec. So aperture is more important to me than IS in this FL range, which is why the 35f2 is more interesting to me than any of the 24-105 zooms. No use comparing this lens to any of the f1.4 L lenses, they are very different beasts.