I'd use it as a new daily driver. I need a new phone with a better camera, screen, and battery, especially for work. Right now, I've still got a N5, so I could use an upgrade!
Me being the power user that I am, I'd install all my go to apps. I'm a casual gamer so there'll be quite a selection of those. I'd love to see how it keeps up with my multiple apps through the day. I'd happily share my thoughts on this with the rest of the users here.
I'd test the audio quality, as FLAC files pair well with a good set of earbuds.
I'd take many photos throughout the day as well as I love photography. A quality camera is something I yearn for.
Ultimately I'd love to see how well it puts up with this busy and ever so broke student's day to day.
I'd love to have the next evolution of the Galaxy line. And hopefully see the return of the SD card slot and the Snapdragon processor as I've really missed them in the S6. And I'd also love to have the emerald green option this time!