I agree with Darrel, but would take it one step further – cornering.

Inertia in general is the kicker with a hovercraft, since you’re basically flying on thrust – there’s no traction involved to steer your momentum around a corner, you have to cease motion in one direction and initiate it in another, making it horribly inefficient, even discounting the blower or fan thrust required to keep the thing off the ground.

Frank-

That’s pretty cool, but one tip of the wings too close to the water, and SPLASH ONE. Also didn’t see it actually land and I supect alot of drag once you hit the water. Keeeping the nose up of course, is key. Sounds like he’s selling them fairly cheap from the price.
I see various types of them on You Tube now called ‘HoverWings’. Thanks for posting that, very neat!. : )

Some have combined aerodynamics and thrust to create a hovercraft that is immune from surface irregularities…

http://www.youtube.com/watch?v=6ih_KBru6Co

The Coast Guard tested hovercraft on the Great Lakes in the mid 70’s and had the rubber skirt tear on rough ice as a result it lost lift and broke through sinking and had to be recovered and rebuilt…

Issues as already stated, but very uneven terrain causes issues as well. The unit ‘floats’ by creating cushion of high pressure air that has to stay fairly even.
If you were to hover across a very uneven surface the air pressure gets unevenly diverted to the high/low areas and causes a drop in float height. The idea has been around since about 1716 and even the U.S. military uses them to replace the old outdated WWII TLC (Tank Landing Craft)

More on them here: http://en.wikipedia.org/wiki/Hovercraft

Speed bumps and breaking after a collision might be an issue as it goes sideways hovering and spins around.