I came from WM6, and I love WP7. It does everything faster than my friends with Android and IOS. I use less than 200mb of data per month, and it's awesome.
		
		
	 
The only time that I used more than a few hundred megs of data in a month is when I had to re-download a bunch of albums to my phone while on the road.  My Surround (and I am totally blaming the hardware for this since it is the third Surround that I have had) decided that it really needed to be hard reset.
I like the simplicity of the UI, coming from iOS it feels more modern and adult.  I have trouble using iOS for an extended period of time now, just because of that.  I don't want semi-transparent tiles that overlay a wallpaper, or whatever that red thing was on the last page... ugh.
But, then again, WinMoPho has like .23% market share or some other absurdly small number and I am not entirely sure where the problem lies.  I have some ideas;
1: The name, Windows Phone 7, is too similar in both name and number to the previous, generally derided, Windows Mobile 6.5
2: The name includes the word Windows, and Windows isn't 'cool'.
3: They only advertise the platform, not the devices.
4: None of the salespeople have used the devices.
5: They hadn't had a standout device until the Lumia 800/900.
As I saw one person suggest on the intartubez, MS should give salespeople a WP7 device to use as their personal device for a couple of months.  Let them really get a feel for it.  The People Hub is amazing.  Twitter and Facebook feed updates in one place, and the contact information automatically pulled from FB and Windows Live.  The email client is pretty good, as is the browser.  IE9m is fast and fluid, with pretty good support (though not the best, that would be mSafari).  The Zune player on the device is good.  Advertise that you can use it eyes-free in the car (swipe up to unlock, left/right to change tracks, no small hit target to worry about).  Bing Search is actually useful, and gives you quick access to things through Local Scout that would have required another app or whatever to get at.
There are a lot of selling points about the device and OS, but no one knows about them.