I have this kit lens for both of my school's 40d, and the IS and USM and the reach is good and the image quality is decent, but, as the equipment head, I can tell you that the lens can be quite a nightmare..
The lens itself is quite heavy (475g) and the zoom ring is just simply "frictionless" aka very loose, zoom creep of course when you point it downwards or moving about, but that is not the scary part yet.
Its 17-85 right? Imagine this, you are shooting.. then your eye is inside the view finder then you recompose for you perfect shot and you need wide!!, you turn from the most tele to the most wide with the loose zoom ring in the heat of the moment asap and you bang the 475g lens from 85mm right back into its 17mm position (Imagine the inertia..), you press the shutter and you hear mirror lockup.. You wonder what happened and the LCD screen says error ** (I forgot the number) "Please check your lens connection"
You unmount and remount, and no more error code, you are relieved, but once you look into your viewfinder, WTF, why so dark one??? You look at the front of the lens and see the aperture ring at its smallest (Not suppose to happen). You desperately point it at an object to shoot and you half press, WTF??? , the focus keeps on hunting back and forth, like vibrating (serious).
I sent the first lens to canon via the school, bill came back $200++

(Warranty over), reason: AF motor spoil. Servicing charge $120 & motor only a few dollars.
The second followed suit not long after :bheart: (SAME EXACT PROBLEM) and now the school refuses to pay for the repair for that.. And now I have a $700 475g paper weight sitting in my school drybox...
Both 17-85 lens were spoilt as it was heavy and loose and frequent banging from changing from one extreme focal length to the other very quickly (very hard to prevent) caused the motor to die [even manual focus also cannot use, cause aperture also stuck]
so... [Sorry for the long story la :bsmilie: , important info for potential buyers] you still want to buy a 1785 :dunno: ??