I've flown several small aircraft with them fitted - a huge confidence booster during flight testing. I should say that I could, but haven't, fitted them on my own aircraft. If on the other hand I was routinely flying over mountains, sea or forest in single engined aircraft I'd seriously consider spending the money. (About £1500 for a system for a small 2-seater).
I think that they are available up to about C172 size. The biggest manufacturer is BRS (
http://www.airplaneparachutes.com/ ). They do work (I have a friend whose life was saved by one to prove it) but the task of installation in an aircraft is far from trivial.
G
[This message has been edited by Genghis the Engineer (edited 14 June 2001).]