I've never flown a 100 foot tail, but I do have one that's 80 feet. When folded flat, it's about 3" wide, and yes, it takes a good 8 - 10 mph, preferably 10+, to lift it off the ground, and fly successfully. Of course, the tail does slow the kite quite a bit, and will drastically limit what can be done with it, however, a tail that large will definitely make a statement in the air, and draw quite a bit of attention. I agree with Rob, though, assuming that your kite can take the wind, and it should (it's rated 3 - 24 mph), you'll have a much better experience, closer to the 15 - 20 mph range. Ought to be a real sight !
Now, the down side of long tails, is folding them up, once you're done flying, especially if that 15 mph is still hanging around. I've found the best way to deal with that, is to have one of those plastic grocery bags in your pocket, and use it as a temporary stuff sack. Then, when you get back home, out of the wind, it will be much easier to deal with.......