is it good for a professional photographer

Hello -- I wanted to add to Richio's comment. I think the choice of equipment is not what will make you different among your colleagues; I think it will be the quality of your photographs. I have a top-end digital SLR, all the equipment I need to take great photos, a wide selection of lenses and so on. Still, I am not a great photographer (I am just "pretty good"). My wife, on the other hand, doesn't know an f-stop from a bus stop, but she can pick up our point-and-shoot camera and compose an image that is wonderful. I'm not saying it doesn't help to have the flexibility and range of an SLR, only that the equipment only allows for the possibility of taking good photos.

The only other consideration for pro photography is the durability of the camera (construction, body material, moisture seal, etc.). I don't know how the Pentax stacks up, but at this price point, it's unlikely to be a super-durable camera. On the other hand, you could have two or three Pentax bodies for the price of what you'll pay for a high-end Canon like the 5D, or a bullet-proof camera like the Nikon D2X :-)

The Pentax SLR cameras have gotten good reviews. If you already had Pentax glass and equipment from a film camera, it's certainly a good choice, unless you expect to put a lot of hard wear on the camera. As Richio says, however, if you are starting from scratch, I think you would find Nikon or Canon is the choice of pros because they have great cameras, and also a very wide line of outstanding lenses, accessories and other gear that give you a great deal of flexibility.