Don't forget that if you install the latest versions of Ambient you will also have to install MUI4 which is also debug enabled and afaik you can't disable this.
I did that yesterday. First installed the latest MUI4 beta, then the Ambient binary 1.43.0 CVS with the installer script.
The speed is fine, I don't see much of a difference really. So if there is debugging enabled in either MUI4 or Ambient, it doesn't slow down the system too much.
However, I have stability problems now. After a certain time playing around with the desktop, Ambient freezes and the "is meditating"-message is displayed.
Further, I get an instant freeze when selecting any of the "About" options in the titlebar menu.
There seems to be a problem with MUI4, since it still shows up as version "3.9" in the Prefs. Is there a tutorial somewhere how to install MUI4 properly and which of the old 3.9-files should be kept?