No actual evidence. Just delayed keystroke echoes. Lost keystrokes, and sometimes the app just goes to sleep. Process Explorer shows no activity.
Firefox does this, and for plenty of sites. It does it for me and it's not key loggers. Firefox is bloated and has gotten a bit slow. So saying that key strokes suffer from slow downs in Firefox is not evidence enough that this site has a problem.
Try this:
Try a different browser, like IE or Chrome.
If you have add-ons installed in Firefox, disable them all and see if that improves things. Then enable individual add-ons one by one to find the one(s) with problems. I know that you probably don't use any web developer tools, but for me, the "Firebug" add-on makes Firefox's responsiveness really suffer.
Maybe big delays phoning home?
Well, I'm not going to turn it off - I need it for the Google statistics that it gathers.
But, yes, it does delay
page loads for just that reason. (Not key strokes. It is not triggered on individual key presses, just entire pages being displayed. Different issue.)
However, the Firefox add-on script called Ghostery will block the GA script for you as an individual user. Ghostery pretty much hides you from the view of all ad bugs and web tracking scripts. (I recommend it.)
Since I installed Ghostery a few days ago all of my web browsing has gotten dramatically snappier.
I wouldn't mind if even most of the users of CCF did this - I am more interested in gross traffic from all sources across the internet.