I had a 6m 2005 Airush Flow C kite and now have a 6m 2008 Torch as my high wind kite. I found both to be great high wind kites, I think most people on hear just talk about what they have read and not about what they have actually done
C kites are not any faster than other types of kites, in fact they are quite often slower than the equivalent sized hybrid kite which is the reason they are better at freestyle. Comments about a C kite being too fast will be true of any 6m kite as 6m kites are fast due to their size.
C kites are also generally more stable and predictable than hybrid kites as they do not have the same range of movement and the c shape is a more stable shape under load.
Finally you ride a c kite with your legs, and when a gust hits you edge harder which will drive the kite forwards in the window reducing power whereas a hybrid will usually just build up even more power so you have to constantly mess about sheeting the bar in and out.
It basically comes down to choosing then correct kite size for the wind conditions, a hybrid will always be "easier" to ride than a C kite when over powered but for competent riders side by side with the correct size kite for the wind conditions c's are a good choice of kite