What you gain - fast, efficient, Unicode aware manipulation. Data integrity taken care for you. Concurrancy taken care for you. Seems too good to be true, I think.
Yeah, but nothing beats editing a registry file with Emacs (which is a joy to do when, for example, a damn game refuses to re-install because it detects some keys in the registry from its last installation).
Going through an UI to do stuff like that would be so Windowish as to not be funny :-)
Lionel