I tried to search for examples of long lens photography, and came across the following collection by Ari Hazeghi of various raptors. He appears to favor the Canon EOS 1D Mark IV, and a 840 mm lens-- probably a 600mm f/4L IS II USM lens with a 1.4x teleconverter.
That's a $5300 body, and a $11500 lens, and probably a damn good tripod. But the images are amazing.
http://ari1982.smugmug.com/Avian/Raptors/White-tailed-Kites/12533571_VQvFQ3#!i=2054472771&k=gmhMB7t
So that's what's possible at that focal length. Compared to that, the P90 looks like a very cheap imitation. Maybe it's useful in the right hands, but for most people it's just a gimmick.