You mean my Stanley Steamer isn't a horseless carriage? Then there's the steam plant I worked on that drove a 4000 ton destroyer at 35 mph... Ok, I'm getting off-topic.
So all seriousness aside, we use MsOffice 2013 at work. (I think--how can you tell any more? there's no "Help | About"! Ok, had to google it, and yes, 2013.) So I tried this preview you mention: selected some text, and moused-over the hieroglyphs, I mean icons. No preview. There's a little balloon that gives a text description of what it means to underline text ("Underline your text", duh), but the selected text doesn't change for this or most other changes. The only formatting change that seems to offer a preview is the font selection. But I never ever ever ever change the font of a piece of text; I always use Styles. So that does me no good. And mousing over the styles (which, as I say, I do use) again does not preview anything, which would be really useful (or preview changes I make to a style). Instead, mouse-over of a style just gives a balloon listing some (obviously not all) of the settings for the particular style, and there seems to be no way at all to preview changes to a style.
Maybe previewing works in Office 365?
And btw, I don't see why previewing wouldn't work just as well with menus as it does (in 365?) with the ribbon. So unless I'm missing s.t., this doesn't seem to be an advantage to the ribbon, it's just a somewhat useful feature that Microsoft happens to have added after replacing the menu with the ribbon.
"Common functions are easier to find for most users..." I guess I'm not "most users", because I don't find it particularly easy to find the functions I use commonly. On the contrary, I have to overlook a lot of features that are, for me, junk: nearly every formatting feature in the "Home" ribbon tab, for example--like I say, that's what God made Styles for. Every single thing in the Design and Mailings tabs, and almost everything in the Insert tab except "Table"--and then, once you've inserted a Table, you have to use an entirely different tab to do anything with it. Whereas everything having to do with Tables used to be accessible from a single "Table" menu. The Review tab has some useful things, but what on earth the Language stuff is doing in there, I don't know (nor who uses it--I'm a linguist, and I virtually never use it). And what's the difference between the Paragraph thingy in the Home tab and the separate Paragraph thingy in the Page Layout tab? I guess if I studied them, I'd figure it out, but it's not intuitive.
In short, I find most of the tabs/ icons in the ribbon useless, confusing, or hard to find. But I'm sure there must be some user somewhere who finds it all logical. You, I guess.
Like them tailfins on your horseless carriage?