I think they're awesome. I am a filmer so I rely on them to get the shot for skiing. It takes a real learning curve but after a while you learn how to do it. 4bi9 has been using them for forever and they are very good at using them
Glidecam seems to be #1 when it comes to non-electronic manual stabilization. The reason they are great for skiing is because nothing is electronic and it doesn't require a battery. This is really important when you are skiing because batteries don't last at all in the cold.There is a bit of a learning curve to using a Glidecam but once you get used to it you can produce some fairly great shots.