I am a big fan of mirror lens and I use 3 of them from 250-1000mm. They are CA free, close focus (relatively), compact, cost-effective and with care you can avoid the doughnut effect (e.g. use solid background). Although that would be difficult in wildlife photography. Thanks to modern in-camera OS and PP software, I can get acceptable IQ even with the cheaper mirror lens now. That was impossible with film camera.
The biggest drawback to me is the really small aperture, which make all of them useful only on a sunny day. Like all other long tele-lenses, tripod or monopod is a must.
Last edited by MJL; 02-25-2014 at 05:43 PM.