OS X Mavericks, which was just announced at WWDC 2013 features some power management and CPU usage improvements that should result in smoother scrolling and better memory management across OS X in general, particularly Safari and Mail.
Some of the largest gripes about Mail and Safari in OS X is the lag, especially with multiple accounts when it comes to Mail and multiple tabs when it comes to Safari. Some much needed improvements to memory management and smooth scrolling should make dealing with multiple tabs when browsing or large threads in Mail should be a much more smooth experience.
