Anticipation is building as Mac fans prepare for the release of Apple’s new operating system, OS X 10.7, aka OS X Lion. Thursday is looking like the big day, with anonymous insiders saying Mac store owners have been advised to prepare for an ‘overnighter’ on July 13, after being asked to perform upgrades on certain showroom models over last weekend. The release is expected to coincide with the launch of upgraded MacBook Air models, which have been on hold while Lion went through its final testing. Although Apple has promised over 250 new features with Lion, the only hints the giant has given about the operating system's release are that it will be some time in July, at a cost of US$29.99.