I've had this lens for 14 months now fitted to a Pentax K100D.
Although the lens is slow compared to primes the Pentax has little noise up to iso800 and combined with the anti shake I can take hand held shots in low light. The need for flash is minimal. The anti shake on the camera probably gives you a couple of stops grace bringing this lens right up there in terms of practicality. I have a number of other lenses but this one hasn't been off the camera since I've had it. Auto focus is quick and accurate. If you look at the distance scale it does tend to front focus at wide settings but I think this is due to the huge depth of field and the camera stopping once it has hit focus. The pictures always look ok even when zoomed in on the pc. Although this is a subjective view I think the results from this lens are better than the kit lens. I've used this lens for panoramas, portraits, action shots and holiday snaps. My 50mm prime might beat it if serious portraits are required but to be honest you would have to take a good look to tell the difference.
The surprising quality of results and sheer versatility of this lens means that it will rarely be removed from my camera.