Flik,
I agree completely. the regs are brakes to brakes and it is fair for people to do it. I log my time from the GPS for 2 reasons, 1) I am to lazy and the GPS makes a perfect record and 2) with well past a thousand hrs i dont really have anything to gain.
Charging people on tach time is just inviting trouble, in my experiance it just makes people abuse the aircraft and skip proper checks.
I twin that I fly regularily is charges on tach time and they wondered why it needed 8 new cylinders recently. A lot of people fly a twin on a budget and at £3 per minute sat waiting around for the oil to heat up or doing a gentle cruise descent is a lot of money to some people and the dont do it. Don't start me on people flying aircraft they cant afford......