I like the K-30 and it feels good in-hand but the couple of problems I have with it are as follows:
1) The upper-right corner thumb rest doesn't need to be as sharply pronounced. It makes that corner of the camera more prone to hang-ups in a variety of situations
2) Bottom edge is a little too sharp, for my personal tastes. It feels solid and easily handled, but again, some times a bit too much is noticeable in a variety of ways
3) The pop up flash housing doesn't need to be as forward and pronounced. Seems to be an added amount of material that could be refined a bit more in overall - hand-to-camera feel.
4) I like the new body texture on the K30, but honestly, Pentax nailed it with the K-5 & K-7. That particular finish feels very durable and has excellent traction, and the sense of the body being metal alloy extends right through the finish to the hand. It's a very satisfactory grip feel and provides a much different confidence in-hand. The squared and angled edges of the K-5, perhaps slightly larger, maybe closer to the K10D size, would be simply dreamy.
The battery grip for the K-5 is what I would consider near-perfect. The thumb rest is nothing short of an ergonomic masterpiece. The button feel, however, needs a bit more indication for the thumb. The relatively flat nature of the surrounding areas makes it difficult at times to get the sense of what button you might actually be trying to use and can require an actual glance to be sure. That can be frustrating but could also be easily remedied to just getting used to the camera feel over time. But, even still, a more pronounced design, perhaps with small braille-type 'nubs' would help and may lend itself to a shorter adjustment time for such things.
I only just recently made the switch to Pentax after years of using Canon, which felt very clunky and, at times, overly large with only 'just-enough' ergonomic design to be utilitarian. The Pentax ergonomics was one of the big factors in my decision, with the obvious aside involving the superior innerds of the thing. Nikon feels good in-hand, and they hit a lot of key points with fit/function, but I'm going to have to kiss Pentax's butt on this one and say that they, by far, are the best form factor designers I've seen yet, in my amateur opinion.
For a Full Frame Pentax, the size of the K10D, which I've previously owned - with battery grip (keep in mind, I've never held a K20 but I would imagine that it feels virtually the same with minor advancements in design) would be my recommendation for a design basis. Less rounded features and more like the K-5/7 and I think you would have a camera that, by feel alone, would set itself apart even further in excellence by design. I'm going to go out on a limb and ask what people would think of moving the aperture preview to a dedicated button on the side of the shutter compartment. On Nikon bodies, the aperture preview button is a perfect default location for one of two fingers that fall comfortably in to that position at all times. Not that I don't like it being on the power toggle on Pentax, but I think that location can be distracting at times and may put unwanted stress and wear on the main power switch over extended time. Any way, open to hearing thoughts on that if any one has experience with Nikon bodies. Canon puts it on the left side of the shutter compartment which has never seemed to be the exact right spot for it to be, although it does fall right under your thumb when holding the camera in a horizontal position. It works, but it's a very forgetful spot for it to be. Nikon's is mint, Pentax's is good but I can only wish for that to be different.
http://photofan.jp/camera/html/uploads/img499e4baf6ba67.jpg
I need more coffee.