Well, feathers and fur are always tricky but I don't think the issue is the 60D. While there are some technical issues with the sensor, I've shot on that camera a lot and you can composite very clean images from 60D footage.
I can't tell what exactly is going on without seeing your lighting set-up and AE workflow, but a lot of the shots seem to have green spill, which is just a lighting problem. Make sure your puppets are at least 6'0 away from your green screen (8'0 is preferable). If you're already doing that, you may have to use a hair light (or "Kicker") on the puppets with a gel that is the exact opposite of green/blue (whichever you are using) to neutralize the green light that is bouncing off the screen and hitting your puppets in the foreground. Roscoe makes those, you can look them up online.
Are you using AE's built-in chromakey tools? Because a 3rd party plugin like
Red Giant's Keying Suite can make a huge difference with things like hair and fur if you aren't. That package is a little expensive ($700 I think), but much cheaper than buying an FS100!
If you haven't already seen them, check out the keying tutorials on
VideoCopilot.net. Andrew Kramer offers lots of great tips and tricks.
Honestly, it's either the method you're using in After Effects or (much more likely) your lighting set-up that's giving you grief. It's possible to get clean composites from footage shot on a $300 T2i, so you don't need a more expensive camera!