No, it's not "obsolete". Rated 5 out of 5 stars
There's this other well-known and much-used add-on--deservedly so--which includes a restart function and icon for the toolbar, but I've been using this one--instead of that other one--for quite some time simply because it offers a better looking icon/button--the other one is pretty ugly in fact. The Quick Restart button is also smaller and fits better on the toolbar--which is where I want it. The only thing that's been "lacking" (appearance-wise, which is subjective at best) is an icon on the File menu (well, it's never shown up there for me, in spite of being there in your sample image--what's that about?). Well, no more:
list-style-image: url("chrome://quickrestart/skin/quickrestart-16.png") !important;
Simple. Effective. Looks good. Thanks!
(Emanuel... you're kidding, right? I guess you never restart unless Firefox tells you to.)