Jakob Nielsen is a well-known guru in the usability world. He has done a lot to bring usability to the forefront of software engineering.

In one of his alertboxes, he does a quick assessment of WP7. 

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From: Jakob Nielsen
Sent: 8/15/2011 9:54 AM
To: Alertbox Announcement List

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WINDOWS PHONE 7 USABILITY TESTING

Last week we ran a series of studies with users of Windows Phone 7, to
update our various mobile training seminars for the San Francisco
Usability Week next month. We still have a month to do the detailed data
analysis, but my preliminary conclusion is that the main design guidelines
for mobile usability don't change: the big findings were the same as for
the iPhone and Android users we also tested last week.

Windows Phone 7 tested quite nicely, though the application store has too
many usability problems. (But so does Apple's store with its clunky iTunes
UI.) Unfortunately, it's still not quite there. I can easily see how v.8
might become a killer, though.

One big plus for WinPhone can be exemplified by this user comment: I know
what this icon means because it's similar to what I see on my PC.

(If you're not so lucky to own the world's most used desktop software,
you'll have to design mobile icons that work on their own merits, and not
all the ones we tested did. More on this in the seminar on Visual Design
for Mobile – 3rd link below.)

A big downside for WP7 is that we now observe accidental activation of the
system buttons, in addition to the problems of accidental touches inside
the apps that plagues iOS and Android. Also WP7 suffers just as much as
Android from the same lack of predictable and consistent use of the
buttons throughout the apps. MS (and Google) needs to crack down on apps
designers who don't understand usability. Much as people deplore Apple's
overly aggressive attitude towards its apps store, there's something to be
said for platform-wide enforcement of a UI standard.

Detailed findings to be reported next month:

  > http://www.nngroup.com/events/tutorials/mobile.html
  > http://www.nngroup.com/events/tutorials/mobile_apps.html
  > http://www.nngroup.com/events/tutorials/mobile_visual_design.html

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