I don't have the Mark ii, but I do own a K-1. I was smitten from day 1.
Things I love: IQ, ergonomics (the camera feels like a glove despite its weight and the control layout is, IMO, flawless), the cross-tilt LCD is
so useful that I don't want a fixed LCD anymore, the OVF is very good.
Things I don't love: it could be
a smidgen lighter. More or less the only thing I could actually wish for, but even then it's not a deal breaker.
That's basically it: the AF is good enough (even AF-C!) for my uses, and I normally don't shoot bursts so I can live with the anemic data transfer rate. The other day (after checking Norm's thread that @Joetitch mentioned above) I tried some tracking shots (105mm @ f/5.6 with the DFA 28-105) or a car that was overtaking us on the highway, I got 15/16 shots focused either perfectly (most) or "good enough" (two or three) on the license plate.
The other thing are the lenses - you mention landscapes, portraits and astro. For landscape, there's no shortage and even the "kit" (lol at that name) 28-105 is so much better than it has any right to be to the point where I'd recommend to get it with the camera, it's a no brainer. For astro the same lens gets you started although there are obviously better options (I'm looking forward to the D FA 21 Limited next year!), and for portraits... well, you get the FA Limiteds, the D FA* 50 and 85, the FA* 85, the D FA* 70-200/2.8, and the list goes on. There's no shortage of good stuff
Honestly, I can recommend it a lot, if you are already interested in the Pentax environment.