I absolutely love this plugin and use it on every client website. Along with a proper editor-style.css file in my themes I can have the page/post editor mimic the front-end styles, eliminating the need to preview a page or post numerous times to get things looking right. Sure that can be done anyway, but with TinyMCE Advanced I can also add commonly used classes to the editor-style.css file, such as theme specific colors or fancy image frames, etc., and have them available in the drop down menu for easy application to the content. This greatly improves the rendered HTML markup eliminating all of those unnecessary inline span styles. Also, users no longer need to remember hex color codes or other complicated combinations to achieve typical results. Just highlight the text and apply the class!
My only complaint is not having an export/import of settings for the button layout. It's truly time consuming and a pain in the @$$ to have to recreate my preferred button layout for every website.
Please add an export/import settings function to make this plugin even better.