As above, fitted mine today that I've had sat around for a while but now seemed the time to get them on!
Didn't take too long. I think it took me longer to get the slightly seized driver's side wiper arm off than to do the whole mod!
As other guy's have said, getting the water pipes off the old jets can be a bit tricky - I found that by warming them with a hair dryer they softened enough to make them much easier to pull off the jet connectors.
New ones quickly fitted in place and plugged in as I have the socket already there. Turned them on and after a short while I could feel a slight warmth in them - helped by the fact that it was freezing outside and my fingers were frozen! lol
So, the next frost will soon determine how useful they are! Certainly worth a tenner and half an hour of my time to find out.