I just wanted to share my latest experience...after believing the 31 and 43 to be overpriced I finally got those 2 lenses and I am very impressed. They are so much better than the 18-135 and also to a 16-50mm (I expect however that the 16-50 was not the best sample...but then I had another 16-50 wich also was not the best sample).
I have read reports you have to stop down the 31 and 43 to get best performance (which is probably true) but the performance at wider f-stops is all ready very good IMO. All, sharpness, bokeh and also color seem very good for my taste.
The lenses are expensive but I am really surprised what the combo of the K5iis and those lenses can deliver.
I follow with some images if I have some subjects where I think its worth to post.