I've got the DAL, WR and AL II version of the 18-55 kit, and find it decent enough if you don't shoot wide open. If you want it at it's sharpest,
shoot between f5.6 and f11 and between 18-35mm. I also use a hood all the time and don't use any UV filter etc.
Interestingly I find the DAL version I have the sharpest and best rendering of the bunch, followed by the AL II. My WR version seems a touch softer across the board. That's sample variation at work. But I've never needed to do any AF adjustment for any of them.
Another strength of the Pentax kit [ as noted by Just1MoreDave] is that many RAW processors (eg DxO Optics Pro and Lightroom) fully support the kit lens, which can help improve its optical performance by fixing issues like chromatic aberration and distortion, and in the case of DxO, addressing some of it's weak spots by doing stuff like deconvolution sharpening of the frame edges.