The DA*1650 is an excellent lens (if you get a matching copy to your camera), but it does have some CA problem when shoot wide open, especially at the wide end. Not a big deal for many users, but some users might not like that.
Here is a indoor testing sample I took last year w/ a friend's DA*1650 and my K10D camera (16mm, F2.8, 100% crop):
It gets alot better when stop down to F8:
I bought the lens about a month back, but haven't really used it yet. Some guy claimed the lens has much less or no CA problem on K20D camera, but not my experience though ...