Been using them for years - can dry the car in one go without wringing it out. (Separate towel for upper and lower panels and door shuts etc)

Much easier if you've got a decent wax layer on the car and use the "weighted hose water" method to rinse your car off.

And use a non bio detergent to clean it. Even better to use the Chemical Guys Microfibre wash:
http://www.cleanyourcar.co.uk/microf.../prod_209.html