I've owned this lens twice and for anyone shooting on a crop sensor camera, I think it's a must-have. Even if you don't use it a ton, it's so small, light and inexpensive that it really doesn't make sense to not have it in the bag or coat pocket or whatever. It's great for video as the STM motor allows for fast, silent AF during recording and the STM is good enough during stills shooting as it's fairly quiet and pretty quick. This lens is unobtrusive and small enough to not stand out, especially when paired with a smaller body like those in the Rebel lineup or the 77D.
I do sometimes find this lens to be a tad soft and find that on my 80D at f/4 with center-point AF and using the "focus-recompose" method of shooting, I get far more consistent and reliable results than with the lens wide open and/or with any other focus method. I have found similar results when using it on my EOS M5 with EF-M adapter.
Where this lens really stands out, for me, is in two areas:
1. Family Stuff: With a wife and baby at home, I'm constantly snapping photos around the house, and when we're out on family walks and the like, this lens is a dream. It's small, light, reasonably quick and gives me a wide enough FOV to include a little background in my images, which is fun. It's a great "documentary" focal length.
2. Tabletop Reviews: I do some reviews of stationery products for my blog (pens, paper, inks, etc.) and this lens' minimum focus distance is right at about 6" which is perfect for shooting small objects in a tabletop setting (you've seen a million of these reviews, I'm sure, where all you see is the reviewer's hands and the item). This lens is wide enough to get objects in frame at arm's length and focuses closely enough to get details in the shots. While not a true macro, it does have some macro capability (albeit not 1:1 and not advertised).
I never leave home with my camera without this lens. If I'm carrying the 18-135 or some other lens, this one goes in a pouch or pocket or whatever. It's too small, light and good to leave at home.