I have the da* 16-50 and it hardly ever comes off my camera. I also have a friend that shoots semi pro and loves his 16-50.

I haven't heard anything about bad lenses, but I am sure that if you buy through a reputable supplier any problems would easily be worked out through warranty. I have heard of people purchasing grey market lenses that are less than spectacular and that really comes down to not always looking for that rock bottom price on everything.