Part of the problem of having such sophisticated toys is that it is never enough especially in photography where most of the performance is coming from the lenses. A good body is essential but having good lenses is a must and why good ones are so expensive.
The lenses "given"; with the K10D (18-55mm/f3.5-5.6 ED and 50-200mm/f4-5.6 AL) are not that bad and maybe better than most "kit" lenses but still, f5.6 when used for portrait is not really good and with bad lighting conditions, you will be forced to use the builtin flash if you want to avoid high ISO (and the other way around).
So a very bright & fixed lens made a lot of sense to me pretty soon. After looking extensively on shops' websites and several auctions on eBay, I managed to get my hands on a Pentax SMC-FA 50mm/f1.4 (left side picture).
Oh boy, this is a gorgeous lens. Some pictures on my Flickr site to give you an idea of what this baby can do. I love it. Fast, nice and very very bright.
So now, I'm into LBA from time to time. I'm already thinking of replacing the kit lens with a Sigma 18-50mm/f2.8 EX DC Macro to be able to do some macro shots (only 1:3 though) and a better aperture all the way. The other contender is the newly-released-for-pentax Tamron SP AF 17-50mm F/2,8 XR Di II LD Aspherical [IF] (yes, that's a mouthful). I have not decided yet. Maybe never.