Rated 2 out of 5 stars
Hibernated tabs get a "data:text/html...xyz</title>" as a tab title (where "xyz" is the last part of the page title - it gets truncated to fit tab width). Their favicon is not removed though - which is a good thing in that it helps you guess what site/page was there before. For some of these tabs, this text replaces their url too, so reloading the tab produces an error.
(some) Tabs with google searches that get hibernated loose their search query part of the URL. The actual URL that was there before the hibernation gets replaced by the domain only part of the URL. Don't know if it is relevant, but my home page is set to Google and is fired on every new tab.
Giving the addon 2 starts for the effort and the idea behind it. The mechanics behind the procedure that fires the tab hibernation seem to work. The code that is executed in order to do the actual tab hibernation though is buggy. I'm confident this will be fixed in time. Keeping the addon disabled for now (in order to be notified of future updated versions so I can give it another spin then).