IN 1967 I was in Ryerson Polytechnical School taking photography. We used Pentax Spotmatics when we did SLR work although most of our work was with large format cameras. Fast forward 15 years and I had an old S1, which was eventually replaced with a Program Plus. IN the meantime I became a photography teacher (HS) and taught photogrpahy for 15 years, at a very basic level. We used only K1000s and film initially. So when the *ist came out I decided to go with that. I figured "I can still use my old Pentax glass. Funny thing about that is, at this point, I have no idea where all that old Pentax glass got to. A couple of divorces will do that to you. ANyway, when I retired (woooo hoooo) I became more involved in photography as a business. I realized back in 67 that you need to have a steady income to survive in photography. Like a pension or something. Pay checks are adequate but they can be few and far between. My original *ist was lost in a divorce. My K100D was traded in on the K-x. I recently purchased a K-5 and am hoping to get a K-5 IIs soon.
Lenses include, the legendary but unsharp 21 ltd, 35 mm2.4 , Tamron 90 macro, DA 18-135, FA 50 1.7, DA 10-17 (this lens is worth buying a Pentax for just on it's own). Sigma 70-300 (until I can find some newbee to buy it) and last but far from least the DA* 60-250 f4, one of the most dynamite lenses on the planet. I also own 3 kit lenses one white to go with the white K-x, also soon to be looking for a new home. Incidently, you won't find the quality of the 18-55 kit, in other cameras or in the Pentax lin-up without spending at least $600 for an 18-135 or a pro grade lens. And the 35 mm and 50 1.4 plastic fantastics will get you a couple of highly rated but cheap primes to start your photo life with.
As for the reasons to buy Pentax.. they don't have an FF, so their top of the line always goes into their APS-c, currently the K-5 II and K-5 IIs. Already the top ranked APS-c system, the K-5II adds superior low light performance, an improved auto-focus system and the K-5 IIs will come without a de-aliasing filter, for improved sharpness. It will be the only APS-c DSLR to do have this, although the Nikon D800e has it as well. The K-5 is already ranked well above many full frame sensors and with the new models coming out before Christmas that lead will increase. Short of a D800 or D600 and about $10,000 dollars in lenses, or a Pentax 645D, with about $15,000 in lenses, I can't think of a system I'd rather have. If you're thinking APS-c you should be thinking Pentax.
Oh and I don't work for Pentax, and neither does anyone in my family. I'm 21limited and I approve this message.
Cheers