After about 1 year:
One of my favorite lenses to use. I normally keep it on my camera when I travel around with it because it is light and small.
It is very good in low light if you don't have anything below f2.0 which rules out pretty much anything more telephoto than 85 f1.8. Of course it is less telephoto than 135 2.0 and bokeh can be somewhat similar in intensity (some qualities are different though) due to its wide 1.4 aperture.
It is very fast to focus, good at small apertures, so it is equally as good at isolating something as it is at keeping almost everything in focus as would be needed in a landscape.
It is easier to use at shutter speeds below 1/60 sec (I've had success with 1/30 sec with some luck even using an APS sensor) because of its small size. I don't think there is a faster lens that is smaller and weighs less in canon's line-up. This is very important when not using a tripod unless you are made of iron.
I have not used the 50/1.8, but you can use the 1.4 and 1.6 and they are both different from each other and the 1.8 aperture settings of this lens.
I have started replacing my slower lenses, and if you are planning on having a nice collection of canon lenses someday, than this one will never be replaced. This lens is perfect for what it is.