"A hands-on preview of the latest operating system coming to Macs: OS X Mavericks. The next version of OS X adds power, flexibility, and features to the existing version, OS X Mountain Lion, but if you upgrade from the most current version, you won't notice much of a difference at first glance."
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips