This lens represents a significant upgrade on the 18-55mm DA kit lens. Infact, I would say they are not really in the same league.
I decided to go for this lens as part of a K30 kit mainly due it’s versatility combined with its weather resistant (WR) capability. What use is a WR lens if you have to swap it out for another one to get the shot? This way I can go walkabout in all climates, have good versatility and be confident my equipment is well protected.