The Good
An entirely new mobile OS, a fresh view of the new mobile operating systems to come with a huge variety of new generation Cellphones.
Features
Really fast and more intuitive than Android. The deep integration of the various social tools was not revolutionary, but it was smooth and better than any other platform.
The user interface is very nice and seems to be very practical. You can easily add boxes, which to me screamed of Android widgets, although less customizable, and access almost any app, person, or phone function you desire in one click. The search on the phone is extremely impressive bringing up different results based on where you are located in the phone’s menus. It is fast, accurate, and overall impressive. Microsoft Office integration., but lacking full editing capabilities, and X-box integration that is not possible (jet) to iPhone and Android.
Microsoft has a very pretty OS that takes some of the advantages of the Apple platform, some of the advantages of the Android platform and puts it all together in a nice looking and very practical user interface. I think Microsoft gave new meaning to the phrase “If you can’t beat em, join em”.
Apps
Microsoft has done well to leverage existing products or services, such as Xbox and Zune, for Windows Phone 7 Series. The new Mobile IE will be based on the desktop version 8 and no longer 6, which should hugely improve the browsing experience and safety. Windows Phone 7 Series devices will also extend to Web services through features like "hubs" and "live tiles." However, I predict that Windows Phone 7 Series poses greater risk to BlackBerry, rather than Android-based handsets or iPhone.


The Bad
The transition from Windows Mobile to Windows Phone 7 could cost Microsoft market share. Today's announcement makes Windows Mobile even less appealing, because something new is coming.
Microsoft is taking too long to bring Windows Phone 7 Series to market. Apple will start selling iPad and is sure to release a new iPhone, and a new Android-based phones and Nokia handsets are sure to ship in April, too.
Features
You do not scroll between home screens, as in side to side, but rather, there is one home screen with all the boxes you want and it is all accessed using “unlimited” vertical scrolling.
No copy and paste, no multitasking.
Apps
Microsoft's core leveraged applications are games and music, where Apple has a huge lead, with consumers and developers, on iPhone, iPod touch and presumably forthcoming iPad. Microsoft's core entertainment push knocks up against Apple's huge lead. Microsoft will offer mobile Office on Windows Phone 7, which I contend is totally unnecessary for consumers, although it's good for extending and preserving Microsoft's productivity suite monopoly.
Apple already has huge mobile application developer lead among closed platforms. Meanwhile, today, Symbian Foundation announced open-source Synbian ^3. Nokia and Intel revealed that they will combine their Maemo and Moblin platforms into the single MeeGo. Like Symbian ^3 -- and Google's Android -- MeeGo is open source. Closed Windows Phone 7 Series must woo developers from closed iPhone OS and three open source mobile operating systems -- Android, MeeGo and Symbian 3.

Sources: http://technmarketing.com/, http://www.microsoft.com, http://www.betanews.com