Will this upgrade improve the performance of my Mac, or degrade performance?.Does the upgrade offer any compelling features?.Major system upgrades are often disruptive, so we have always recommended a very conservative approach to applying them. Unless, that is, you have a complete, bootable backup of your Mac made before you upgrade. If you upgrade your OS only to discover that a critical third-party application or peripheral doesn't work right, you could be really lost when you discover that it's impossible to downgrade to a previous OS. So Apple has shipped the next major operating system, and you're excited to upgrade! But are you ready? OS upgrades offer the thrill of new features, better performance and bug fixes, but they can come at a price - your time and potentially your productivity.