Apple promised us a software-rich WWDC this year, and the company delivered. While iOS 7 looks set to be the biggest change in the company's mobile offering since the original iPhone, OS X Mavericks teased the latest refinements to Apple's desktop platform. Not so flashy as iOS 7, perhaps, or as sweeping in its changes, but no less important as Apple continues to join together the dots between its platforms. Mavericks is still a work-in-progress, but Apple provided us with a recent build of the new OS X to get to grips with the highlights - and pick out the key changes - ahead of its full release this fall. Already, there are signs that Mavericks will be another must-have OS X upgrade; read on as we get to grips with the new heart of Mac.