They grow up so fast these days…
GeForce Experience is NVIDIA's software package, often bundled with their driver updates, to optimize the experience of their customers. This could be adding interesting features, such as GPU-accelerated game video capture, or just recommending graphics settings for popular games.
Version 1.8 adds many desired features lacking from the previous version. I always found it weird that GeForce Experience would recommend one good baseline settings for games, and set them for you, but force you to then go into the game and tweak from there. It would be nice to see multiple presets but that is not what we get; instead, we are able to tweak the settings from within GeForce Experience. The baseline tries to provide a solid 40 FPS at the most difficult moments, computationally. You can then tune the familiar performance and quality slider from there.
You are also able to set resolutions up to 3840×2160 and select whether you would like to play in windowed (including "borderless") mode.
Also, with ShadowPlay, Windows 7 users will also be able to "shadow" the last 20 minutes like their Windows 8 neighbors. You will also be able to combine your microphone audio with the in-game audio should you select it. I can see the latter feature being very useful for shoutcasters. Apparently it allows capturing VoIP communication and not just your microphone itself.
Still no streaming to Twitch.tv, yet. It is still coming.
For now, you can download GeForce Experience from NVIDIA's GeForce website. If you want to read a little more detail about it, first, you can check out their (much longer) blog post.