Take a look at the last 5-6 reviews on the 28-135 lens. The ratings are pretty low topping off at 3. If you look at the earlier ratings, they were mostly 4's and 5's. Has Canon's quality gone down for this lens on recently built ones? Are the reviewers jumping on the bandwagon and forcing the ratings of the lens to plummet?
Anyway, I've had mine for more than 3 years and it has been a gem. I can't even count the number of times that the IS has saved the day.