Quote Originally Posted by Squidward
The only shortcoming that I can foresee is that you cannot open it up to blur the background like you can with a 50mm f/1.4 or f/1.8 but you can improvise and get almost the same results.
1.8 is also good for low light situations. I use natural light, a majority of the time, so being able to go higher than 3.5 often comes in handy. Such as in a church at a wedding when flash is usually not allowed.
And I'd rather use a higher aperture than a higher ISO to avoid as much grain as possible.

Low light situations.