Since I started seriously getting into photography I've had experience mostly of 3 Fuji digital cameras and 2 Pentax SLR's. I have shot a bit with a Canon AE-1 as well as my SPI/SPII and a K1000 at one point that belonged to a friend. Also with a K10 and a K100, and some sort of professional Nikon once for a brief second. (Sorry, can't remember which at this point.) A good buddy has a Canon DSLR, so I've looked at that close up too. I've also examined the demos in the area, all the major brands pretty much, except Pentax. You can't find a Pentax DSLR here if you try.
By far I prefer the Pentax brand to any other. My SPII is my favorite camera bar none and when I finally do get a DSLR I'm definitely going Pentax even if it means I have to take a trip to go buy one.
I'm a total Pentax snob and proud of it.
I might upgrade from one camera to another, but I really doubt that I'd ever go with another brand by preference. I seriously covet the K-7, but will probably settle for a K-x eventually, at least for starters.
I do absolutely get the Pentax love thing. There is something about using a Pentax that is totally unlike using any other camera to me. It has something to do with hand feel, I think. Some cameras I pick them up and no matter how good they are supposed to be they just don't feel right in my hands. I've never felt that with any Pentax analog or digital. It's like they fit just perfectly. On top of which I know they're excellent cameras and there's the old glass factor.
People always ask me why I'm so rabid about my Pentax cameras.
I always say "Pentax? What's not to like?"
One of these days I think I'm just going to put that on a T-shirt...