I wouldn't try furling one with strong winds from aft of the beam.

The Leisure Furl in the boom system is probably the best regarded version of the ones that you're asking about, Ron. It's a far cry from the old "around the boom" furlers of ages ago.

I HAVEN'T personally used a Leisure Furl, but I've considered them, examined the options in the past, and spoken with a lot of people that have them. If I were going to get one, I wouldn't get a motorized one on a "normal" sized yacht -- too much can go wrong with a power winch.

As Todd (and others may have) noted before, you can get a better shaped sail with special battens which will function a lot better than a vertically roller furled mailsail. Also, as others have noted, if things get FUBAR, you can always drop the sail down and flake or lash it down.