Meaty demo that gives you a good taste of the final game. Once I understood how to use it effectively, the "One More Fight" mechanic is great. It's free and you can easily play it for 8 hours+!
The second to last boss fight is brutally hard. Even harder than the final boss of the demo on the hard setting. Ugh, such bad memories.
I'm glad that there are bonuses to transfer over to the full version, but some of them are really tedious, like filling out the beastiary. You have to fight each non-boss monster something like 100 times. Yuck. The bonuses are nice, but not worth seeking out in the demo, unless you are killing time until you can get the full version.
(Bravely Second [Demo] was obtained as a free download from the Nintendo E-shop)