Sly (GitHub: Darsain / sly, License: MIT, Bower: sly) by Darsain is a library for scrolling -- it can be used where you need to replace scrollbars, or where you want to build your own navigation solutions.
The author has paid particular attention to performance:
Sly has a custom high-performance animation rendering based around the Animation Timing Interface written directly for its needs. This provides an optimized 60 FPS rendering, and is designed to still accept easing functions from jQuery Easing Plugin, so you won't event notice that Sly's animations have nothing to do with jQuery :).
Sly's author also sent in FPSMeter. When working on graphically-oriented projects, it's sometimes useful to display the frames-per-second of animations. FPSMeter (GitHub: Darsain / fpsmeter, Bower: fpsmeter) measures FPS using
WindowAnimationTiming, with a polyfill to patch in browser support for most browsers, including IE7+.
FPSMeter can measure FPS, milliseconds between frames, and the number of milliseconds it takes to render one frame. It can also cope with multiple instances on a page, and has show/hide methods that will pause rendering. It also supports theming, so you should be able to get it to sit in nicely in your existing interface.