I've heard some say that the image quality isn't any better than the 40D or 50D, possibly due to the high number of mega-pixels crammed onto the APS-C sized sensor.
Also, a common complaint about the 60D, is that it's smaller & made with more plastic, than it's predecessor the 50D. In other words, it's closer to the Rebel series than the 50D was. This isn't really a knock against the 60D....it's just not what people expected when it first came out.