Love it or hate it, the full-blown Sense UI is incorporated into a number of smartphones from HTC. Users of phones like the EVO 4G are quite familiar with Sense which sits on top of the stock Android UI. For those that prefer the cleaner stock Android UI, your only option is to use a custom ROM which has been designed to remove Sense.
Microsoft, when designing Windows Phone 7, decided to be quite a bit more strict when it comes to UI design. Microsoft's guidelines for smartphone OEMs don't currently allow them the same freedom as they have with Android. As a result, the user experience across numerous WP7 smartphones from different OEMs is very consistent (this is the exact opposite of Android-based smartphones).
However, that could be changing according to comments by HTC's Drew Bamford who is in charge of HTC's User Experience division. “Our expectation is that we will be able to do more over time," Bamford explained in an interview with Forbes. “HTC’s goal is for the Sense experience to span all of our products.”
Bamford comments are understandable -- with many smartphones coming out sharing the same hardware specs, screens, and pricing; features like Sense can help allow one product to standout out versus another. However, Sense flies in the face of what Microsoft is trying to achieve with WP7 which Bamford acknowledges.
“Microsoft has its own goal of consistency across Windows Phone 7 products. I think it comes down to working closely with Microsoft to do as much as we can.”
Should OEMs have the freedom to muck with WP7 however they see fit, or should Microsoft force OEMs to adhere to its UI guidelines? That's the $64,000 question.