Microsoft previewed Windows 8 today at the BUILD conference. In his keynote, Steven Sinofsky, president of the Windows and Windows Live Division at Microsoft said, “We reimagined Windows. From the chipset to the user experience, Windows 8 brings a new range of capabilities without compromise.”

It comes with a personalized lock screen that shows unread emails and other app notifications, the ability to see apps and content “in a glance” on the start screen, it lets you pick files you want to send or share from one place, it has fast touch browsing and large buttons on the touch keyboard, and a thumb keyboard. Here are some screenshots of this stuff:

Other key features, as highlighted by the company include:

Touch-First User Interface

To me, the most exciting feature sounds like the part about “turning on instantly and running all day on a single charge.” Since using Chrome OS, Windows start ups have never been as painful.

The developer preview release will be available tonight at 11PM Eastern. It includes a 64-bit (x64) build with development tools to build apps and a 32-bit (x86) or 64-bit (x64) build without development tools. It also include a suite of sample apps, which are just illustrations of potential apps, not apps that we intend to ship with Windows 8).

The buzz is pretty positive so far. Here are some tweets:

Engadget has a hands-on demo video of the Samsung Series 7 Slate running the new OS:

Are you excited about Windows 8? Do you plan to get a Windows 8 device? Let us know in the comments.