With all the recent positive press with the Microsoft phone OS, there has been very little negative feedback. Other than from the Mac guys, but anything Microsoft is horrible, sight unseen. Here is an article that hits on some of the points that I agree with, and mentioned the other day.
Windows Phone 7 Series may prove to be a bad choice for enterprise customers due to lack of control over the device. Also a lot of Microsoft’s fortified technologies can’t talk to a lot of newly evolving Muktware (Open Source) technologies.