I think Xootr makes a killer folding bike too, called the Swift. Check out the Folding Bikes sub-forum.

They don't fold very small, but they're fast.

When I need to get on a rush hour train, I use my Dahon Curve D3, which folds a lot smaller than the Swift. (important for bringing on the train)

Kick scooters wouldn't be very good for a commute longer than about a mile, I'd think. Not as small as a kick scooter, but a lot faster and more road-worthy.