WestFalcon, great topic. I was gifted this lens sometime ago. I started out with Xti and have used all the Rebels. I am currently using T2i and 60 D. I started out with the classic kit (18-55 mm) and now am using the 18-135 IS. I like the spread of the zoom range. I think that the 17-55 2.8 is a great lens but the wider range of 18-135 is a plus for me. I speed is not a detriment working with the IS system. This system makes you want to forget the tripod. IQ is great with this lens and the price is great. Canon had refurbished for less than $200. It's not an L less costly also. JR
Note that the newer 18-135 mm STM lens is supposedly much improved over the older 18-135.
I used the newer STM lens fairly extensively with my T4i for video and stills. It is a pretty decent quality lens. It focuses quickly and accurately in photo mode. For video it also lets me use my T4i in place of a video camera in many situations when I would have used a "camcorder" in the past.
It is the only non-L lens that I have actually used and decided to keep in 20+ years, along with the 40mm STM. Not a bad investment if you can get it as part of a kit. A little pricey at $400+ if you have to buy it separately.
Though better than its predecessor, even the STM version isn't the sharpest duck around, but it focuses quickly and silently in video (more so than the 40mm I've found).