The only feature in Ultimate that looks interesting to me it the MUI.
But here's my beef with the MUI: why the hell is it limited to only Ultimate and Enterprise? Let's say you are a family living in Quebec. Some users of your family prefer English, some prefer French. Right now, the only sensible thing to do is to buy an English version and a French version, and have one computer set up for English and another set up for French. But what if there is a common shared computer on which you want both languages? Sorry, you gotta be an Ultimate/Enterprise user for that!
Okay, to be fair to Microsoft, this is better than how it was in 2K/XP, where MUIs were available only to volume licensing customers (and to MSDN). The idea back then was that MUIs made it possible for companies to support multiple languages in a more uniform way: deploy a standard base English version to all machines, and then on certain machines, install the MUI (plus, this ensure that every machine had the base language on it, so that the IT staff would still be able to navigate a machine that was given to a Spanish-speaking employee). But MUIs are pretty useful outside of corporate mass deployments, for multi-lingual immigrant families, for example.
Anyway, for me, the reason I care about MUIs is that they are necessary for testing software in different locales (especially in RTL locales like Hebrew or Arabic where the rules of layout can get really funky). But I have a MSDN subscription, so this isn't a problem for me personally (but even though I have access to free Ultimate licenses, I still use Professional and use Ultimate only on my test/debug systems, simply because I don't need the other features in Ultimate).
I really wish Microsoft would just kill the Ultimate SKU, make MUIs a universal feature (most immigrant families that would benefit from MUIs are not going to be able to afford Ultimate), and fold the other handful of rare and exotic Ultimate features into Professional. Remember back in the good old days when Professional was the top SKU? And then they could kill the Starter SKU, too. They can keep Home Basic as an emerging market product, but would it really kill them to make Home Premium the bottom item? HP is already the lowest that you can get at retail, so why the heck have an even lower Starter edition that--get this--doesn't even let you change your wallpaper?
PS: There's a bit of Vista history here: in Vista, the editions were not supersets, and Vista Business did not have Media Center and a few other "home" features found in Home Premium. So back in the Vista days, if you wanted both "home" features like Media Center and business features like Remote Desktop, you must use Ultimate. But with Professional being a superset of HP, Ultimate makes much less sense now for Windows 7 than it did for Vista.