The are several issues with this addon, though, as it doesn't restore it completely.
Firstly, is that the compatibility issues addons have with Australis still exist since it's merely a userstyle rather than an actual restore.
Secondly, it doesn't restore the addon bar nor the menu bar, both which are still gone. Thirdly, it still draws the menu button in the title bar.
There are several other issues this addon doesn't resolve as well, however, these are the most common issues.
It was time they moved to futuristic UI, we live in 2014 not in 2004. It is easier and pleasing to use too.
For most of what Australis brings, I'll agree with you. Most of what they did, I've been using via extensions and XUL userstyles for years.
...but I still think it was stupid to remove the add-on bar and change the menu to a panel full of toolbar buttons. I like putting rarely-used (like AdBlock Plus and Greasemonkey) in a second toolbar which can be toggled with Ctrl+/ and not even Chrome is crazy enough to switch to a menu which has no keyboard shortcut hints and may confuse accessibility software.
(The annoying thing is, if there's one menu I need an editor for, it's the context menu... which isn't helped by their "let's just use the toolbar editor" redesign.)