Quote: The quality is definitely not as good as the primes though, but decent for a zoom.
Of course it is hard to rival the Limiteds in terms of image quality, but the 50-135 comes dangerously close, even when you are a pixel peeper. Especially during longer trips or vacations, it is hard to justify all the lens changing when you can keep only one lens attached. And 2.8 is not bad, especially with the K-5.
So when my main purpose for the day is photography, I go with 15,(35),43,77, but especially when there are others who would have to wait for me, the DA* is just more convenient.