Windows 8 is potentially the biggest overhaul of Microsoft's client operating system ever, introducing a radical change in the user interface accompanied by a new application model, plus numerous technological changes under the hood.
A great deal is riding on the success of Windows 8. This is the first version of the platform where touch-screen input is ubiquitous, aimed at delivering Windows-based tablets capable of taking on Apple's iPad and stemming the decline in PC sales as buyers favour other devices.
However, Microsoft has to deliver this without alienating existing users and without breaking compatibility with the huge installed base of current Windows applications, the latter being especially important for business customers.
We tested the RTM code on several systems, including a Samsung Series 7 Slate PC with a 1.6GHz Core i5 Processor 2467M and 4GB memory, and a Lenovo ThinkPad X201 laptop with a 2.4GHz Core i3 processor and 4GB memory. Our impression is that the new user interface will discourage many Windows users from upgrading, as it delivers little improvement in user experience for users on desktops and laptops over existing versions of Windows.
That said, there are many new features that could make Windows 8 a compelling upgrade if you can forgive the UI, including built-in Hyper-V virtualisation, Storage Spaces and Windows To Go, which runs from a USB memory stick.
The Windows 8 code was made available for Microsoft TechNet and MSDN subscribers to download on 15 August, but will not be generally available on new systems and in retail until 26 October.
[UPDATE: Microsoft has released updates to the RTM code and built-in applications since this review was first published - see page 5 for details.]
Unlike earlier versions of Windows, there are relatively few different editions. The standard edition for PCs will simply be Windows 8, while Windows 8 Pro includes more advanced features for professional users, such as virtualisation support and the ability to join a Windows network domain.
A third version, Windows 8 Enterprise, will be available only under Software Assurance licensing to corporate customers, while the ARM-based Windows RT version will only be available integrated into devices.
For this review, we used the RTM version of the Windows 8 Pro edition, but most of the details will be applicable across the board regardless of edition.
The most obvious change in Windows 8 over previous versions is the user interface. Originally referred to as "Metro-style" and now simply known as "Modern", this borrows heavily from the user interface of Microsoft's Windows Phone platform.
Thus, the main Start menu screen comprises serried rows of tiles, each representing an application. These tiles are 'live' in that they can show updates, notifications and other content, such as new email messages, the latest news stories or photographs, while touching a tile launches the app.
This user interface is clearly aimed primarily at tablet devices, and is designed around fingertip gestures, such as swiping in from the edge of the screen to bring up options and access other functions.
For example, swiping in from the right edge displays a bar of what Microsoft calls "Charms", giving access to key system functions such as search, the sharing function, devices and settings.
Swiping in from the left allows you to go back to a previous screen, while swiping down from the top edge inside an app takes you back to the start menu and swiping up from the bottom gains access to more apps, including legacy Windows functions such as the Control Panel.
For users without touch-screen computers, the same functions can be accessed using a mouse or keyboard functions, such as the Windows key.
Of the Charms, the Search charm provides context-sensitive search, so that keying in text within the email app will show results for messages containing that text, for example.
The Share charm is intended to let users share information from within applications, such as sharing photos to their Facebook account, but relies on the share 'contract' being supported in both the source and destination apps.
The Devices charm gives the user quick access to any available devices, such as an external display, while Settings provides access to some (but not all) configuration settings, and is also where the power-off and network access controls can be found.