I like the 18-55 STM simply because it is light. It is also really quiet and can perform well, and has a close MFD. I was gifted a EFS 17-85mm IS USM that was destined to take its place. It was even made in Japan, unlike any of my kit lenses. The sad news is AF went out on it. I'd like to get it working again, but it's not under warranty. It seems a little redundant as well. But it was a step up from the 18-55mm IMO. On paper the 17-85 doesn't look like much, but seemed to get good results.
I used the 17-85 for quiet a while and actually quiet liked it. Lots of distortion but a convenient focal length range.
With regards to the failed AF on your lens, I had a similar problem except it was with the aperture mechanism. Turns out a flexi-rigid cable had split due to fatigue. I managed to repair it myself, but its not a job for the faint hearted.