So I've been running Mavericks on my Mid-2007 iMac since it was released without any issues.
I've managed to update all of my Apps (iWorks, Aperture, Logic X etc) apart from iMovie because my machines graphics card wasn't supported (ATI Radeon HD2600 Pro with 256mb RAM).
Fair enough - its an old machine so I thought nothing of it.
Strangely today however, having just updated Aperture to Version 3.5.1, iMovie also updated!
I'm now running iMovie 10...