Well, I finally made the leap and upgraded from my *ist DL to the K10D.
I was seriously considering the K20D. As I was posting my DL for sale on craigslist, I saw a deal on a K10D that was too good to pass up. The difference in money between this gently used K10D and the K20D was too substantial to ignore, and the K10D gave me 95% of the upgrades I was looking for: pentaprism finder, 11-point selectable AF, weather seals, battery grip.
I feel like it was the perfect move for me right now. The K10D matches how much more serious I've been getting with photography, without breaking the bank. It also means I might be able to afford to upgrade sooner if Pentax make a move with a DSLR that includes 24fps HD video. As a filmmaker, the possibility of using my Pentax glass on a DSLR to shoot movies is VERY tantalizing. I know if I didn't have an investment in Pentax already, it would be very hard to resist the Nikon D90. But I'm happy to wait a little longer for Pentax to get into that game. (They came close with the K20D at 21fps... if only they could have pushed it to 24fps, with longer clips.)
As for the K10D, I am SO impressed. It's a major step up from the DL, and having handled a lot of different Canikons over the past few years, the K10D is solid. I'm having a blast with it, and look forward to my first shoot. I have a request for some family portraits and I can't wait to use the K10D.