Hi Nate!
Considering I have taken photos with this camera almost every day since almost the day it was released, I think I'll take a shot at this

Keep in mind, though, the only other DSLR I've used at any length is the K100D.
It is pleasurable to use on a daily basis. It's a bit larger and a bit heftier than the K100D, but I wouldn't call it heavy; it just feels substantial. It's sturdy; I've dropped it exactly once and under the worst possible conditions you can imagine (fully-extended tripod; concrete ground; nothing to break the fall) and with no ill effects that I can find. The weather-sealing works: I have used this camera in tropical storms, snow storms, sand storms.
Many of the buttons are customizable, which I find useful. For instance, I'm likely to forget to change ISO, so when I look at the top LCD, I see the ISO and not the shots remaining - I have to hit the "OK" button on the back to see that. All of the other buttons seem intuitive and easy to use. The more advanced models have more buttons for individual functions, but I've never felt that "digging through the menu" makes me miss a shot.
The AF can leave something to be desired in low-light conditions; the newest models have addressed this. Still, in 90% of my shots, the AF does its job. The speed of the AF varies by lens. When I have to focus manually, the viewfinder is large enough and bright enough to do the job. I'm almost 95% sure I used manual-focus for this shot this morning (uncropped shot of a hoverfly with the D-FA 100 Macro):
http://www.flickr.com/photos/aravis121/3641163192/
It takes AA batteries, which was a HUGE plus for me. I travel to countries occasionally where reliable electricity isn't a given, and I'd rather buy 10 sets of regular AAs and get the shots I want than to have a proprietary system. That said, I have 2 sets of 4 Eneloops that have been responsible for something like 100,000 shots and I just now decided to get replace them. I have only ever had to resort to regular AAs twice, I think - but once was during a wedding! It's for this reason I've never desired the K10D or the K20D, although the KM is tempting. The K-7 might make me a believer in proprietary lithium, though...
The thing I like least about it is the lack of multiple exposures in-camera and its size, but these are minor quibbles given the advantages. I don't want to sound too much like a fangirl, but I really love this camera. I take it out every day and usually carry it in my hand the entire time, anywhere from an hour to eight hours. At this point it's more like an extension of my arm.
In terms of picture IQ, I could not be happier.
--
Keitha McCall
Pentaxian and Snapshot Shooter since April 2007
http://flickr.com/photos/aravis121/
http://www.ascenicworld.com