Bad Pentax experience

Wanted to give the K5 and the 16-50/2.8 a try today. I ordered from Amazon. Took a few shots this afternoon, near and far, tried different settings, all good. Finally returned to the computer to check the files and ... was pretty disappointed.

The JPG output seems mediocre to me. Really nothing special. The images were soft and the 16-50/2.8 was visibily decentered. I didnt even like the bokeh at 50mm f2.8.

So Pentax afficionados... did I get a bad sample or what? How is the consensus on the 16-50/2.8?

I expected it to be in the same league as Nikons 17-55/2.8 but obviously my copy was not.