Nothing wrong with the Pentax, I just feel like it's better to spend a bit more and go for a camera from one of the big three. If you're just wanting a basic SLR and will stick with the kit lens for a while, it's probably fine, but if you decide that you really like photography and want to expand you might find yourself wishing that you had spent a bit more to begin with.
This is the biggest thing when considering a new DSLR, and the reason I feel you shouldn't go Pentax, but Canon/Nikon.
You buy a DSLR, you like what the kit lens does, but you've found that you like landscape photography, portrait, macro, or what have you...and you want to spend $450 to buy a good lens. Now, you don't just have money in the camera itself, you have a significant amount of money in the lens, also.
If you go Canon/Nikon, you can get yourself that $600 camera, and when money permits, get a new lens in the style of shooting you like (mine happened to be portrait...something I didn't think I'd ever like, seeing as I don't like having pictures taken of me).
If you were to go Pentax, you can surely buy a lens that accomplishes the same goal, but it won't do it nearly as well. Also, consider the fact that the lens production has moved to Vietnam, and the body production to the Philippines. A little research shows that when they moved production, the quality of their products decreased.
In contrast, Nikon and Canon are the worlds largest optics manufacturing companies. They spend and make many, many billions of dollars a year in selling high quality digital imaging products to high end customers like government and hospitals, as well as satellites and telescopes. All the biggest optics needs are done by these 2 corporations. They are the fastest to innovate, and their consumers reap the benefits.
The Nikon/Canon lenses are of the best quality, and you'll find that you will eventually switch over to one of the two. Why not start off with one, allowing you the freedom of being able to just choose a second lens rather than having to worry about selling your camera, finding a good deal on a new one, and then after all that finally getting a new lens?