I have had my K5 for almost 3 years and my DA*300 for 3 1/2 years. I mainly do bird photography and this combo has served me well. From time to time I have looked at what the other guys offer, but I always found myself looking for what I already had: light weight, comfortable ergonomics, rugged build, excellent high ISO performance, and fully implemented TAv mode. Some people have claimed that 300mm is too short for bird photography, but I prefer to hike out in the natural world and work to get as close as I can to my subjects. So the DA*300 has been the perfect match for my K5. Here is an example:
http://remotesensingart.com/Pentax16/BarredOwl_K549166small.jpg
shot in near darkness at 1/160, f/4, ISO=5000, cropped to 1760x2200 and downsized for the web.
I would appreciate better AF-C performance, although I have gotten many BIFs with focus spot on, such as this Red-shouldered Hawk:
http://remotesensingart.com/Pentax6/RedshoulderedHawk_K528420small.jpg
But I have missed some BIF shots with the K5. I was tempted by the K5IIs and its reported greatly improved AF-C, but decided to wait for the next body. Assuming the rumored feature set of the K3 is real, I will add it and keep my K5 so I can go out with a second body and a shorter lens such as the DFA100. Also assuming the long-promised 1.4x TC is finally released, I will get that as well and then have what I would consider to be an unmatched combo for bushwalking photography.
LPA