How useful are headlight wipers?

How good are headlight washers/wipers at keeping the headlights clean?
My winter car, a '86 BMW E30, had wipers until one of the previous
owners removed them. The wiper motors and nozzles are still there but
not connected (see picture). I've thought about getting wipers and wiper
arms and connecting everything as it used to be. However, I'm curious to
how useful they actually are. I realize that they're more than a
gimmick, but how much more?

Thanks,

Ulf

http://members.roadfly.org/ulf/IMG_1192.jpg