Frame rate? About 5fps is ok for me- although nice to have 8.
For me- maybe not for everyone- it's all about the megapixels!
All I want is my D300s, rebuilt with 24mp (or 44 if Nikon feel like it).
I can never get close enough. I'm an aircraft guy- not a birder- but I suspect 'croppability' is what both the BIF guys and I would appreciate. Also, I use my camera like a telescope (or a notebook) as well as for photography.
I want resolution above everything. Any damn camera can take a good photo- heck my old Oly E-1 took fantastic pics with its 5 mp sensor.
Sure, I struggle with atmos effects on hot days and all those mp wont help, but there's times when I simply run out of resolution on the 300s.
Ultimate IQ and resolution/ croppability must be better with more pixels. I don't mind 12mp for close in stuff. I've no plans to change my D700.
But for far away or small subjects, the more megapixels the better!