Ribbons are about easy discoverability, and fundability (for things you already know about). You have a series of labeled tabs, and in those tabs are a series of grouped controls. The most common ones, with very recognizable icons (such as bold/italics/underline) aren't labeled and just have an icon... the more obscure ones, with less descriptive icons (such as "Insert Citation") are given a label as well.
Having used Microsoft Office, OpenOffice, and KOffice a decent chunk over the 2000s, of the three I preferred using KOffice the most (OO had an absurdly slow start time). And then I had to use Office 2007, which introduced the Ribbon. In no time at all, I already preferred the new interface, and was using features I didn't even know existed (such as managing citations). The Ribbon creates tiered, logical 2D groupings of controls. With a toolbar, you sort of have 1D groupings of icons... which is fine with a half dozen icons, but becomes worse and worse the more icons you introduce.
When I've talked to various technical people, they'll often bash the ribbon... but then they tend to always opt to use ribbon-based interfaces instead of non-ribbon. Based off the non-technical users I know... they tend to be able to do more with post-Ribbon versions of Office than pre-Ribbon versions (they'll use a wider feature set, instead of just basic font editing, like would happen before).