I have used furled leaders. I can't find it now, but I have a simple set of instructions for making your own. The only material you need is a piece of planking about 6 ft. long, 6 long finishing nails, a j-hook and drill or dremel tool.
Anyhow, I really liked furled leaders for all the reasons stated, but one of the negatives that has not been pointed out yet is when you get snagged, whether in-stream or in a tree. If you yank the snag loose and the leader gets stretched and then breaks free, the recoil of tension will make a temporary mess out of the furled leader and you will need to untwist it. Perhaps a minor inconvenience, but when you are in the trees as much as me, it makes you think twice about using them as a standard, all-purpose leader.