I currently have four camera systems, and I'm determined to get down to one or two. I travel a lot, and compactness is important. I tried Leica, but it's not working for me, and I'm going to sell it off. And the fact is, I'm tired of dragging my Nikon system around -- the D3 and the D300 are great cameras, but for what I do, there's not much that can't be duplicated by the K-5, which I've had for a couple of weeks now. The biggest problem with Pentax, IMHO, is the lack of a flash system as sophisticated as Nikon's. If I were a company like Hoya, I'd find a way to make the Pentax (accidentally?) compatible with the Nikon flash system...I suppose if you need huge fast glass, then you'd also need to go to either Canon or Nikon, but that's way more specialized than anything I will ever need. I guess the ultimate answer is to understand what you need, and then buy to that standard, and that's what I'm trying to do.
So the K5 (which has really fine high-ISO abilities and enough resolution for my style of printing) will compete with the Panasonic m4/3 as my camera of choice: I have a GH1 and a GF1, with several lenses (most recently added the 100-300) and I'm looking forward to the GH2 this spring. If the GH2 is as good as Michael has said it is, I may leave the Pentax behind, too. But I do like the Pentax; it's compact, handy, and has exceptional image quality. IMHO, it's right there with the D3 in quality, and it's much easier to move around the county. I have a fairly complete system in the overhead bin right now...
JC
JC