Kadee's have transformed my enjoyment of this hobby. Shunting, coupling and uncoupling using magnets has been so much fun and engaging. I now spend much more time 'rubik cube' shunting and marshalling wagons in yards than main line running, and even marshalling older non-uniform coaching stock.
The addition of Wheeltappers DCC sound chips which their F12 auto-uncoupling function is an added bonus but not necessary. F12 synchronises a short nudge of the loco back and forth with notching sounds and coupling noises for use with both uncoupling and coupling. I've found only one delayed uncoupling magnet is needed per yard if placed strategically due to the delayed uncoupling action (i.e. uncouple over the magnet but push wagon past back into a siding of choice). This negates the need for multiple magnets.
PS: I agree with Graham, gearbox mounted whisker spring kadee's are more consistently reliable for uncoupling than NEM kadee's due to the greater rotational movement of the former (i.e. shank pivots in gearbox in addition to knuckle rotation). With this in mind I have started to cut away NEM pockets on some of my 2 axle rolling stock and replace with gearbox kadee's.
PS2: http://www.wheeltappersdccsounds.co.uk are the same Irish sound projects sold by DCkits. They are not done by LegoManBiffo who does all the UK stuff.