From Mikel:If you've used Chimera on the Mac, and you haven't tweaked it already, you must enable pipelining.

1. Quit Chimera
2. cd ~/Library/Application Support/Chimera/Profiles/default/<random>.slt/
3. Append these lines to prefs.js:

     user_pref("network.http.pipelining", true);
     user_pref("network.http.proxy.pipelining", true);
   

4. Restart Chimera

The perceived speed difference is incredible (although obviously it's limited to sites where pipelining would help).