Top tech headlines: Roundup of tech buzz

Hot topics in the tech blogs for the week ending September 16 include the preview of Microsoft's forthcoming Windows 8 operating system, Facebook's new Subscribe button, Windows 8 reviews, leaked iPhone 5 case designs, and lower than expected earnings and shipments for RIM.

Microsoft shows off its Windows 8 preview
Microsoft unveiled a preview of its forthcoming Windows 8 operating system at its BUILD developers conference. The concept behind Windows 8 is that it is a touch-first user interface built around Microsoft's iconic Metro style. The web is mostly bubbling with enthusiasm about the new OS, labeling it the 'ultimate Windows platform' but some blogs are criticizing Microsoft for showing off a "half-finished" product that won't be ready for consumption until (the rumored launch date of) 2012.

Facebook unveils Twitter-like follow button so strangers can subscribe to your updates
Facebook started rolling out a 'Subscribe' button that gives social networkers the ability to share information with people, even if they are not mutual friends. The subscribe button also provides granular control over updates posted by new or existing friends in the News Feed. It enables users to choose which specific types of updates (photos, life events, status updates, or games) they want to see from which friends in their feed too.

500,000 downloads of Windows 8 as reviewers post their hands-on reviews
Microsoft CEO Steve Ballmer revealed that downloads of the developer preview build of Windows 8 hit 500,000 during the first night it was available. He told developers that "We still have a long way to go with Windows 8" and reemphasised how the new OS was a completely re-imaged Windows. Hands-on reviews of the OS on tablets and PCs were posted on the net and included comparisons to Apple's iPad iOS 5, the "sad" new Blue Screen of Death and Xbox Live on Windows 8.

Leaked iPhone 5 case designs and rumors
With just weeks to go before the rumored announcement of the iPhone 5 (or 4s) leaks have started to appear everywhere on the web. The latest rumors suggest the iPhone 5 will have a "radical new design" thanks to renders of iPhone cases that were spotted after briefly appearing on popular accessory maker Case-Mate's website. The New York Times reports that "an engineer familiar with the new iPhone said it would be fairly different from the iPhone 4 — including on the inside." Apple is rumored to time the next generation iPhone announcement to coincide with the first ever Macworld Asia Expo which will take place in Beijing from September 22-25.

RIM posts lower than expected earnings and disappointing tablet shipments
It's been a rough week for BlackBerry manufacturer Research In Motion (RIM). The company posted lower than expected earnings and announced it had only shipped 200,000 PlayBook tablets. All Things D said both RIM's sales and earnings were at "the low end of its forecast, and below what many analysts had been expecting." Business Insider reported that RIM's initial shipment estimates for the tablets were up at around 600,000 to 700,000 and adds that Apple shipped 9.25 million tablets in its last quarter.