I picked up a used copy of the 15-85 a couple of months ago for about $300 to use with my 77D. The lower grade lenses just were not sharp enough for the high-res sensor, in my opinion. I didn't want to carry a lens as large as the 17-50 F/2.8, so I gave the 15-85 a try. So far, I'm pretty happy with this lens/camera combination for a vacation or "walk around" system. I'm really enjoying the ability to lift the shadows and rarely have to do HDR now.
The wifey and I spent several days in Orange County CA last week, just wandering around and soaking up the sun. It was a good chance to try out the new gear. Overall I'm very pleased with the lens. Sharpness is good and I'm not seeing any chromatic aberration, even in the corners. The relatively small aperture is offset by the camera's ability to shoot at high ISO when needed. I assume the IS is helpful too, but I don't pay a lot of attention to it.
Here are a few shots from the trip. The sharpness you see here is less than what I see in the originals, so factor that in as you view them.
This first image is from Mission San Juan Capistrano. i lifted the shadows quite a lot. ISO 100
This is from inside the one of the dimly lit buildings at ISO 12,800. I had to do some noise reduction in Lightroom.
The Corvette is in the Marconi Museum, ISO 1600 with a little noise reduction in Lightroom
A classic car in the Lyon Air Museum ISO 200, with some doctoring in Lightroom.
Just a bit of street photography at the California Adventure theme park.