Hello, I'm concerned too by this problem.
The Finder takes 100% of CPU but the system runs normally.
What I've seen is that it calms down when some applications are hidden or minimized, like Firefox, iTunes, Mail, Preview, TeXShop,
Anyway, when these are shown back, the overrun restarts.
I think the problem is from a module shared by all these applications by Finder.
The Finder itself doesn't seem to use it, though I believe that it has something to do with display (as when the window is hidden the CPU calms down) and that I must have not found the correct file type to show in Finder, or something like that
madprog