Just buy the 18-135 and end your waffling...
At f 5.6 snd f8. its better than the DA* 16-50 at twice the price from 24mm to 50mm. IN fact of the lenses I've compared it to , only the 50 1.4 is better than it edge to edge anywhere in it's range. Other lenses have better center sharpness. None have the excellent border sharpness the DA 18-135 has at 24 mm and 5.6. And the 18-135 has excellent or very near excellent center sharpness all the way through it range.
The guy who gave it a bad reviewed must have written the review on a Monday morning. His conclusions aren't supported by his own data, and I can show you on his site with his own numbers where he's given lenses with much worse numbers, twice as good ratings. Don't get fooled. It has it's weaknesses, but when you consider how excellent it can be used to it's strength, there really isn't another zoom lens comparable to it in a K-mount, at least as far as I can see.
If someone wants to post better numbers at 24mm for a K-mount lens prime or zoom, or better numbers for a zoom @ 50mm,I'd certainly like to see them.
My DA 18-135 images.
The lens is worth buying just for it's performance at 24mm f 5.6 and f8. Everything else is bonus.