Q
There are many discussions with samples on PentaxForums. The Q requires amazingly sharp lens to give sharp images at high magnification: top quality fast primes. Diffraction sets in early, already visible at f/4. To get the effective focal length that accounts for the crop factor, multiply the focal length by 5.5: a 300mm on the Q frames like a 1650mm on a FF camera.
The best Q tele shots i've found online are with a Borg fluorite telescope.
I'd be very interested to know what gives better IQ and reach: a telescope with Q, or digiscoping with Q and lens. I'd bet on the telescope, but digiscoping also gives you AF.