At a launch event today in the US - featuring an appearance from actress Jessica Alba - Microsoft trumpeted the phone software that it hopes will compete with Apple's iOS and Google's Android.
A range of new smartphones running Windows Phone 8 are to go on sale on Friday (November 2), including models by Nokia, Samsung and HTC.
Existing Windows Phone customers will not be able to upgrade to the new operating system, but will instead get access to a Windows Phone 7.8 version, offering some but not all of the features. Microsoft has not yet indicated a launch date for this.
Microsoft's head of Windows Phone, Joe Belfiore, today took a swipe at iOS at the launch event, accusing Apple of creating a rigid format featuring rows of icons with its operating system, a model that, according to him, Google replicated with Android. Belfiore feels that Microsoft's system offers "a truly personal phone experience".
As with previous Windows Phone generations, the unique selling point is 'live tiles': icons that can be placed on the homescreen, and then will update in real-time with new information.
The latest software allows users to adjust the size of these icons, such as reducing them down to thumbnails, or enlarging them so that they stretch across the whole screen.
Users can arrange the 'Start' screen as they choose by 'pinning' their favourite apps, music, games and people to the homepage. Themes on the OS can also be tailored across 20 different colours, including cobalt and crimson.
Microsoft has engineered the Windows Phone 8 lock screen so that it can be integrated with Live Apps. For example, Facebook can be linked to the software so that it displays information such as status updates while the phone is locked.
The biggest issue facing Windows Phone in the past has always been apps, as this is where the software is the poor relation to iOS and Android.
Microsoft says that it now has 120,000 apps in the Windows Phone store, a fraction of its competitors' libraries, but the company has signed up 46 of the 50 most popular apps for Windows Phone 8.
New apps coming to the platform include Angry Birds Star Wars, Cut the Rope Experiments, Disney's Where's My Water, LivingSocial, Temple Run, Urbanspoon and Pandora, the internet radio service which Microsoft will offer in early 2013 to customers for an entire year with ad-free music.
However, the absence of the Facebook-owned photo-sharing app Instragram will be disappointing to many users. Instead of Google Maps, the software again runs Nokia Maps.
Other new features on the OS include Rooms, a way to share and chat with a group of other users in a mini, private social network.
Users can share calendars, shopping lists and photos with only those who are invited. The service supports access with users on other smartphone platforms, such as the iPhone, although they don't get the same experience as on Windows Phone.
Kid's Corner is a way for parents to give their children access to their smartphone without them doing anything they shouldn't.
The app, praised at the launch event by Alba, gives kids their own closed interface with only apps approved by their parents. They also get their own camera roll.
Data Sense allows people to manage their mobile data consumption to maximise their tariff plan. It compresses Web images, defers data tasks to free WiFi where available and automatically adjusts the phone usage when the user is close to their data plan limit.
Microsoft claims that the average person will get 45% more web browsing on their data plan by using Data Sense.
Windows Phone 8 also features greater integration of Near Field Communications, including a wallet application for storing debit, credit, loyalty and membership card information for wireless payments and transfers.
The Microsoft-owned Skype will be an "always-on" experience on Windows Phone 8, enabling users to make and receive Skype calls in the same way as a regular phone call.
Friends and family members can be Skype-called direct from the People Hub, and Skype is always on and ready to accept a call.
Microsoft has also integrated Office, Xbox Games and the new Xbox Music service into the operating system, as well as Skydrive, with all users offered 7GB of free cloud storage to place photos, videos, documents and other files.
A range of phones has been produced for the Windows Phone 8 launch - the Windows Phone 8X and 8S by HTC; the Nokia Lumia 820 and 920; and the Samsung Ativ S.
The handsets will go on sale in Microsoft stores and selected retailers this Friday (November 2), with SIM-free pricing to be confirmed at the launch.
Mobile network EE will exclusively offer the Nokia Lumia 920 in the UK from November 9, including a version that supports EE's new 4G network that goes live tomorrow. EE will also offer the Windows Phone 8X and 8S by HTC.
O2 will offer its customers the Nokia Lumia 820, Samsung ATIV S, and the Windows Phone 8X and 8S.
Three will range just the two HTC handsets, while Vodafone will offer the HTC phones and the mid-range Nokia Lumia 820.
From later this month, retailer Phones4U will sell the Nokia Lumia 920 and Lumia 820, along with the Samsung Ativ S and the Windows Phone 8X and 8S.
The Carphone Warehouse will offer the Nokia Lumia 820 and the two HTC Windows Phones.