Pentax DA 18-55 F3.5-5.6 WR
The Pentax DA 18-55 WR is a pretty good lens. Its useful 18-55mm focal range, good build quality, above-average image quality (for a kit lens), and weather sealing (a feature unheard of at this price range) make it a pretty sweet deal.
Centre sharpness is excellent wide-open. Stopping down to f/8 increases the edge sharpness to very good levels.
Compared to the DA* 16-50 F2.8:
The DA* 16-50 F2.8 is definitely a better lens, however the general consensus is that it does not warrant its high price, especially when there are alternatives from Tamron and Sigma that are cheaper yet offer just as good image quality. In addition, the DA* 16-50 has had issues with failing motor drives.
It's cheaper to buy both a Tamron 17-50 F2.8 and a DA 18-55 WR than it is to buy a DA* 16-50 alone. In this scenario, the Tamron will serve as the primary lens, with the DA 18-55 WR as a so-cheap-that-it-might-as-well-be-disposable backup in case it rains.
The DA 18-55 WR has an impressive minimum focusing distance of 25cm, giving a magnification of 1:3. This allows you to take some decent macro shots.