I worked at a sailing school with CDI furlers on all of the 20' keelboats. They worked well and were simple, but I wouldn't want one on a larger boat. The flexible foils, while fine for short, small headsails, are bound to have issues on large luffs. Also, even on the little boats, when the wind really picked up, they became hard to furl due to friction on the drum.
We chose to get a Hood roller reefing unit - cost about $650 and is very well made, robust, and works flawlessly. We don't use it to reef; just furl.
~Aaron N.