I don't think anyone is saying it's that much different. To me, that's what makes it suspicious. Sense, MotoBlur, & TouchWiz all fragment the android platform, break/change certain view widgets, and lag behind the major release. If you've ever written an android application, you probably remember how you have to remember to set the fonts, colors, font sizes, and just about every property of every widget just to make sure your app looks consistent. WP7 being brand new has the same advantage that iOS does. You don't have to guess what you're UI will look like on someone's phone because they all have the same environment. On Android, it's absurd.
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I'll take this a step further and say that this is at least one of the reasons that there aren't as many high quality apps in the Android Market. Though, there are obviously several more.
People have positive feelings toward W7P even if only because it is novel UI-wise. People don't have positive feelings toward Nokia's UI work... let's just say that.
Oh yes I agree, the UIs are horrible. I think Nokia wants and needs to make current Nokia users happy with the new phones by implementing "Nokiaisms" (even though the underlying OS will change).
Sense and Touchwiz fragment the UI and generally lag more compared to stock Android UI. On top of that, it takes them ages to port the UI skins to the latest Android version which delays the upgrades by several months
It's not the UI which is fairly high-level code. See the Android source code for the default Launcher application. What takes time is porting a new Android distribution and kernel to that custom hardware of yours, test all of your hardware-facing kernel code again completely, and make sure your kernel ABI can still talk sensibly with your userspace counterparts since things and APIs might have changed since the last Android version.
