Office 2011 loads some components in the background after the app loads. It is much faster to load than 2008. It is also much faster at doing just about anything, including crunching large sets of numbers.
They may all be under the same "Microsoft" banner, but the MacBU has been a separate entity since it was spun off in the 90s. This was done to get some focus on their Mac products, instead of having them be created by the same bozos who write Office for Windows. MacBU has been integrated back into the Business Group, as of a few weeks ago. This means that they work alongside the Office and Exchange guys, which has enabled them to do massive amounts of compatibility work. Compatibility is not just the file formats - TextEdit supports doc and docx. And frankly, the file format itself is largely irrelevant. No matter the format, the application needs to handle the data the same way. And the new versions will. The Mac guys have made substantial contributions to Exchange, and as a result, Outlook for Mac+Exchange do things that were not possible before. Many of the business-oriented features were not available in Entourage because they were built into the Windows OS. Well, the Mac guys have gotten many of them built into Exchange via the Exchange's Business Logic Layer.
You would be dumbfounded by how serious Microsoft are about this version. I spoke to the product manager about it a week or so ago, and Office 2011 is massively improved over 2008, in ways you wouldn't imagine. VBA is not just back, it's the exact same version as Office 2010 (Office 2004 had an older version than the equivalent Office 2003).
I see people making cracks about the paper overlay test. That whole "everything in exactly the same place, to the very pixel" thing is so non-trivial. You think it's like, duh, but even Adobe doesn't get it right, and they're the desktop publishing/printing specialists.
So, clearly you know for a fact that the images on those slides are not 100MB apiece.
The Ribbon is of course optional. It is also not the same Ribbon that people lambasted in Office 2007. Even Office 2010's Ribbon is not the same as the one from Office 2007. I've used the Ribbon in all the Office 2011 apps, and found it useful and reveals features that I didn't know were even present (eg: setting permissions controls on emails sent from Outlook 2011). It's on by default, and unlike Windows you have the option to turn it off due to the Mac's persistent menubar, but do try it before you dive for the preference panel. And Resolution Nazis are boring.