No, Chrome's extensions are basically the same as GreaseMonkey scripts (at least, that's the frequent comparison I've heard). Firefox's extensions have the full power of XUL and can radically change the browser.

engage beating a dead horse here

The lack of functionality in Chrome extensions is why I (and judging from the comments I've seen in most Chrome vs Firefox threads, many other HNers on Firefox) refuse to switch to Chrome despite its much touted speed. Until I can get Pentadactyl and TreeStyleTab, its just a downgrade in usefullness.