Tracks:

Mushroom Cup:

Toad Circuit:

Generic starter track, first use of glider.

Daisy Hills:

The track with the hot air balloons. Features long gliding section and rams.

Cheep Cheep Lagoon: First water level, shown off at E3 and demoed multiple times.

Shy Guy Bazaar: Arabian themed with multiple routes.

Flower Cup:

Wuhu Loop:

The track that is one long lap. There are giant cars you need to dodge.

They really want to emphasize those cars.

Mario Circuit:

Contains a lot of coins for unlocking parts.

Music Park:

Music themed (obviously), features pirahna plants and music notes that shake the ground.

Rock Rock Mountain:

Another air themed track, has a lot of shortcuts to take.

Shell Cup:

Luigi Raceway (N64)
Bowser’s Castle 1 (GBA)
Mushroom Gorge (Wii)
Luigi’s Mansion (DS)

Banana Cup:

Koopa Beach (N64)
Mario Circuit 2 (SNES)
Coconut Mall (Wii)
Waluigi Pinball (DS)

Characters:

They confirm that there are more characters than the sixteen released. I’m personally hoping for Waluigi and Dry Bones to round out the roster.

Items:

Fire Flower is on a timer.
Last item in the lucky seven is a mushroom (as I predicted!)
Tanooki tail deflects shells back. Not sure if multi use.

Link