As for what it actually smells like,
4Gamer describes identifying the fragrances of roses, lavender and vegetation while viewing establishing shots of the village, as well as an oceanic smell during fishing scenes. Scenes of Nikki herself were enhanced by the smell of her perfume.
Despite there being a surprisingly large number of scents during the 2-minute experience, they apparently did not mix or linger, and there was no sensation of mist hanging in the air or something being sprayed around you.
Gamer.jp reports that “the scent is emitted from a nozzle at the bottom of the monitor, and the amount is adjusted to prevent multiple scents from mixing, taking into account the distance from the viewer.” The Grid Scent seems to be equally effective at eliminating scents as it is at creating them.