I've bought a 50mm f1.7 A series lens to take nice portraits of the kids, after reading a few threads like this one, and I've been amazed at the difference in the photos that I've got to the kit lens.
Here is one example, with a 100% crop to show what I mean.
User Photo Gallery - People User Photo Gallery - People
I'm amazed at the colour, contrast and ease of use of this lens on the K10. It's really changed my views on what lenses I'll try to get hold of. I've ordered a split prism focus screen to help with the manual focus, and have just bought an M series 135mm lens to try out as well.
Best Wishes to all in the 'A club',
Nick.