It's as easy as it can be right now. You literally just download a program, plug in your phone and press the start button. Takes about 5 minutes or less. The tool is Windows only right now but a Mac tool is on the way. You can revert it to factory non jailbroken form via iTunes at any time.
It's the little things really. Whether its setting Google Maps as your default maps app or installing 3D Touch on a non 6S device. A lot of the stuff in iOS right now like widgets, control center, pull to refresh and even the app store were all available via jailbreak forever now since like iOS5. There's a ton of tweaks out there and rejected apps like GrooveShark, Popcorn Time or Flux (I don't use them), things to speed up animations, improvements to existing apps (Instagram/Snapchat). There's a lot of tacky and unnecessary stuff out there but the best part is just picking and choosing whatever you want. I personally like to keep it minimal in the tweaks department unless its something I really want.