I recently picked up a DA 50-200 WR with intentions of using it mostly with my Qs. I previously had a non WR version, but gave it to a friend along with my K100 DS and my original DA 18-55 so she'd have a versatile overall kit.
I think the DA 50-200 has gotten something of a bad rap by reviewers and users. I've always liked the lens and thought it was easily one of the top three xx-200ish consumer zooms ever released for Pentax (along with the A 70-210 f4 and the F 70-210 f4-5.6. The DA has a wider FL range and is considerably smaller and lighter than those other two, and is, IMO, an excellent consumer grade long tele zoom.
Most diving birds, in my experience, are pretty shy, and rarely get close to shore when anyone's around on the shoreline. They like to keep their distance -- usually 30-50 feet at least, and this makes them hard to shoot unless you have some pretty big glass on a DSLR. My max FL setup is a 300/2.8 + 1.4x TC + 1.7x AFA to get 714mm f6.7 (and almost 9 lbs, not including the tripod and gimbal). At 200mm on the Q, I get a similar FOV at about 1/2 stop faster max aperture and the whole thing, with Hoodman loupe and OEM adapter weighs about one lb total. In the past, I've gotten better images with a DSLR and the big glass, but they were really not that much better, and it took many times more effort for such a small gain in IQ.
These were shot in jpeg, PP'd to taste using Topaz DeNoise and InFocus, and downsized to 1024 on the long side. I used Av priority and set the adapter aperture to about "1". All were handheld, some standing unsupported, and some sitting with my elbows braced on my knees. SR was set to 200mm.
I'd say, considering how brutal the Q is with adapted lenses, this is pretty good performance. I'll not hesitate to use this lens with the Q if I need to sacrifice a bit of reach from the DA 55-300 and save a little space in the bag.
Scott