Are there any pro wildlife photographers using the Pentax DA★ 300mm? I have spent a week searching for anyone who is using Pentax kit in wildlife photography and who is getting paid for their work.
Aditya Panda has touched on it (twice), and finds DA★ 300 quite superb but simply too short for wildlife photography. Unfortunately, the small user base means it's hard to design quality supertele lenses with competitive price. Also, judging current lens lineup and omission of full-frame body, Pentax seems to avoid expensive market niches. So, very likely wildlife photography using Pentax gear will remain challenging in near future.
UPDATE: Pentax has announced and presented on Photokina 2012 a 560mm f/5.6 lens. While not from DA★ series, it will have AW weather sealing. There's also a focusing motor built into lens, but currently the specifications don't claim it to be a silent (SDM) one.