Yes there are three current Pentax digital SLRs, plus the previous models, so I can't really comment much on "the Pentax digital", except to say they can produce excellent images as can a Nikon, Canon, Fuji or Sony. The K100d and the K10d have built-in "anti-shake" systems which some owners find very helpful and some never use. Previously Pentax were often thought to have brighter viewfinders than the competitors but now that is changing e.g. Nikon's viewfinders are much improved. The K10d has weather sealing, again that might be important or it might not. The 6-megapixel models (K100d, K110d and *ist series) all use the same Sony sensor as Nikon's 6-megapixel dSLRs, while the K10d has a 10-megapixel sensor. All have a "crop factor" of 1.5x as do Nikon and Sony; Canon's factor is 1.6x for comparable cameras although Canon also offer larger sensors including "full-frame" 35x24mm. There is a good range of lenses and flashes for the Pentax system, though not as widely available as Canon or Nikon. Unlike those two companies Pentax do not offer a camera designed for professionals, which is not the same as saying you can't use their cameras professionally.
In short, look at their system of cameras, lenses, flashes and accessories, and look at the ones to be released shortly. Do the same for Canon, Nikon and the others. Some Pentax users are going to tell you how wonderful they are and some other folks are going to give you the opposite view, and ultimately you're going to have to make the choice based on which system you think suits you best.