Well, the user response was rather spirited, one might say. Thousands of responses and votes, and just a few days later, Microsoft updated their position.
We would like to reinforce that for this forum to work optimally we would need users to create unique suggestions each with a single idea. This particular suggestion item has many varied ideas and because of that we aren’t able to infer what is the most important to this forum. Please reallocate your votes to other suggestions that have a single idea.”
Now one might view this as an attempt to walk away from the idea, but the operative wording for "users to create unique suggestions each with a single idea" and to “reallocate your votes to other suggestions that have a single idea” is what is important. If you browse through the UserVoice site, you can see that a huge portion of the responses were veritable laundry lists of features being requested. It would stand to argue that the Windows Phone team was looking to aggregate the most common feature requests. Unfortunately, rather than setting up a single-selection survey, they positioned themselves to be on the receiving end of a tidal wave.
So, if you had to pick only ONE feature what would it be? In the Windows Phone 7.x ecosystem that is not such an easy question to answer.
sources: Windows Phone UserVoice, WMPoweruser