I was using the Pentax accessory flash unit when testing the K-5; I assume the
built-in flash would have produced similar results. (Perhaps not, since it's so small that it does not produce much light. Unless the subject is quite close to the camera, the photos may not seem too bright. But I used the accessory flash when testing AND shot some scenes with the Nikon D7000 and the Nikon flash unit; the latter were fine.)
By default, the K-5 produces soft images. I find Smart Sharpen in Photoshop or Elements is ideal for getting perfect sharpness. (+1 in-camera sharpening really helps too but sharpening in software provides amazing results.)
Of course,
when you downsize an image to Web-use size, it seems to turn to mush. Here is a K-5 photo that is larger (
without in-camera +1 sharpening). I DID sharpen it in Elements since there's no point in displaying a soft photo.
PeterKBurian's Album: Pentax K-5 Review photos - PentaxForums.com