Actually I've been using it all the time ever since it came out in beta. Being able to set it to record certain games automatically so I can share something funny or report cheaters after the fact is amazing.
No need to fiddle with OBS to find some instant replay like thing, remember to start it and then edit them in another piece of software. it's all right there, built in to Steam, and so easy to use that I often trim and save clips during gameplay.
Not necessarily. It's directly integrated into the program and platform that most PC gamers use, meaning it doesn't require any third party software and is probably easier to use. Personally, Geforce's solution stopped working reliably for me a long time ago.
It's a really interesting tool. With games integrating with it so certain things show up on the tracker can really help you find the clips you're trying to export out.