It's not a scientific review, I just want to share my thought about EF-S 18-55 IS.
It's been widely reviewed in many top review sites, Photozone and SLRGear to name a few, that it's an (super) excellent lens.
Sure, it's excellent buy for it's price. The IS alone makes it a steal. It produces better images than old 18-55 and more resistant to flare.
With very cheap price, I have the luxury to try a couple copies before traded them in local market.
The last one I owned, its AF motor was dead after a few month of using. I thought I'm not lucky to get bad built copy, until I saw a couple of ads of this lens in the local market with dead AF.
I think we just can't get good image, built, and price at the same time.
For around $100 (used), We'll always get what we pay.
While the image quality is decent (not excellent), good IS, the built is far from reliable.
After my experience with this lens, personally I don't recommend to use the lens as a workhorse on travel, unless you have backup. The IS and flare-resistance would be handy for low-light city shots.
I'd like to have another copy of this lens if there's one floating around in very appealing price, but I would prefer a good built lens in similar range as my main gear.