Originally posted by gastch I love my K-3. I have the 50 1.8 a Sigma 17-50 and Da* 50-135. I got Pentax for the WR and because its the brand my grandfather used and I have his old lens and K-1000. These days though I am finding it harder and harder to justify the wait and hope that they or a third party will release more lenses in the longer ranges or even their newer glass. I would be happy if the 150-600 in either of the 3 formats was available in k-mount. Looking at the used market it would be a whole lot cheaper to just go Canon or even Nikon as used glass for them is even more affordable than used glass for pentax. It doesn't even seam like Ricoh knows which way they want to go with their delays and releasing new "pro" lenses with DC motors (one is delayed) and then releasing another one that's a rebranded Tamron. I have no problems with a re branded Tamron but there seems to be no consistency here for coming out with glass for the full frame. Everytime I say thats enough and get ready to start over I think no I'll wait abit longer and see if things change with the third parties releasing their newer lenses in k-mount when the FF comes out. To be honest I'm not holding my breath. Why do we even bother? End of morning rant.
It all depends on what your specific needs are also what your budget is. To switch systems, it means you have to sell your current equipment at a discount and buy another brand all over again. You will lose money in this exchange. The question is can you afford to do that.
I came from Canon digital to Pentax thinking that some of my Canon problems will be solved. Well I gained some and lost some. One of the things that I lost was the availability of third party lenses and a much bigger selection of Canon lenses.
My suggestion is to make a two column list of what each system offers. Tally up the pluses and minuses of each system and see who comes out ahead. I kinda of thought that Pentax glass is cheaper than Canon but that is not the case when you factor in some excellent third party lenses (Tamron and Sigma). In that case Canon or Nikon or even Sony come out ahead of Pentax in overall cost of the system and the selection of lenses they offer. If you shoot serious sports you will need FAST super telephotos (600mm f4 and 400mm 2.8). They cost a bloody fortune but Canon and Nikon have it and Pentax does not.
For most shooting situations, Pentax offer enough lenses to produce professional results. For me Pentax offers plenty of lenses and pro bodies and ergonomics second to non, to justify my switch from Canon. For me, it was nostalgia. My first camera ever was a Pentax MX film camera. I had issues with Canon so I decided to go back to my original brand of camera. The first camera was the k5IIs and now the K3. Both of them have been spectacular cameras producing professional results. So, I can wait to see what happens with the FF. I am not about to switch again, after all the grass is not that green on the other side anyway!