My experiences using them follows:
We have three ways to get around on them: kite, downhill trails, and motorized (gas and electric).
A favorite run is the 16 mile all downhill dirt fire road that goes off backside of Mnt Palomar nearly 5,000 vertical feet! Name Harrison Grade. Here in Pauma near San Diego.
You actually start often above the clouds! The beginning is a downhill switchback paved road through pine forest, cool and dry (first 2 miles), the road becomes sand and continues to switch back occasionally breaking open views and then back into smaller birch and pine groves, another couple miles the road becomes less steep and open now you can see 50 or so miles the shoulders of the trail drop off. No pushing needed but occasional stops to rest, speeds around 10-35 mph. Not fast compared to biking but fast enough to feel the wind and get a good rush. About 7 more miles the road turns to a grey gravel, becomes a bit harder to stop on this surface, but its very smooth and quick, the last 2.5 or so miles we cut through an orange vineyard which is also downhill, cries crossing through a leaf/grassy carpeted type surface (squishing oranges as we go), and finally ending at a main road, dusty, wiped out but with lots of adrenalin still pumping.
We have done this over 10 times now with great results. Also have skated down Big Bear, and Mammoth (slight misshap on that trip resulted in 4+ days in the hospital due to hitting a nasty deep stash of pumice (collapsed lung, broken ribs - but still almost made it to the bottom of Mammoth). But that was a while ago, and I have learned bit on how not to fall since then I hope (fall upslope, and crouched).
Also have been doing a lot of kite skating which so smooth and fast. This is just so relaxing. Low tide and wind coming in from the Oceanside sea making graceful loops out into the shallow surf and then back up the beach.
Some days there is sea weed all over the place which is kind of fun to roll over other times it is smooth as glass and the skates really start picking up speed. I use a 5 meter kite. Lots of power even in low wind, its very cool and amazing how much pull a power dive generates.
That one movement where you turn and the kite jives over to the other tack its 0-20 in about 2 seconds, kind of a slingshot effect. Its truly a strange combination of sailing and skating. The kite is on 75 feet of line so its way out there, far away but still you feel every thing the kite feels.