We knew that NVIDIA had an impending driver update providing DirectX 11 performance improvements. Launched today, 337.50 still claims significant performance increases over the previous 335.23 version. What was a surprise is GeForce Experience 2.0. This version allows both ShadowPlay and GameStream to operate on notebooks. It also allows ShadowPlay to record, and apparently stream to Twitch, your Windows desktop (but not on notebooks). It also enables Battery Boost, discussed previously.
Personally, I find desktop streaming is the headlining feature, although I rarely use laptops (and much less for gaming). This is especially useful for OpenGL, games which run in windowed mode, and if you want to occasionally screencast without paying for Camtasia or tinkering with CamStudio. If I were to make a critique, and of course I will, I would like the option to select which monitor gets recorded. Its current behavior records the primary monitor as far as I can tell.
I should also mention that, in my testing, "shadow recording" is not supported when not recording a fullscreen game. I'm guessing that NVIDIA believes their users would prefer to not record their desktops until manually started and likewise stopped. It seems like it had to have been a conscious decision. It does limit its usefulness in OpenGL or windowed games, however.
This driver also introduces GameStream for devices out of your home discussed in the SHIELD update.
This slide is SLi improvements, driver-to driver, for the GTX 770 and the 780 Ti.
As for the performance boost, NVIDIA claims up to 64% faster performance in configurations with one active GPU and up to 71% faster in SLI. It will obviously vary on a game-by-game and GPU-by-GPU basis. I do not have any benchmarks, besides a few examples provided by NVIDIA, to share. That said, it is a free driver. If you have a GeForce GPU, download it. It does complicate matters if you are deciding between AMD and NVIDIA, however.