The reason for the CPU usage is due to the status "barber pole" animating. Since it seems that this animation routine is built into OS X, the issue is not really an issue with Camino, but more with Mac OS X itself (you can see similar behavior in other applications which also use the barber pole animation).
To resolve the issue of CPU usage, all you have to do is remove the status bar from the BrowserWindow.nib file. This file is inside the Camino.app bundle (control-click on the app for the Show Package Contents pop-up), on the path Contents -> Resources -> English.lproj -> BrowserWindow.nib.
To edit this file, you will need to have the Developer Tools installed (or XCode if you are fortunate enough to have it). Once open, simply double click on the "Browser" icon in the BrowserWindow.nib window, and then select and delete the status barber pole widget.
Save, and restart Camino, and you should find it to be much quicker during page loads. This might also affect other areas of performance, such as browsing pages that contain Flash content.

