Hobbs sucks. At one airport I was held for 45 minutes due to commercial traffic. At least I wasn't paying for it though.
In oz I once hired a Duchess and was charged via an airswitch - basically I paid for all time spent about 50 kts! Definitely the best way. 2 nd best it Hobbs.
I don't like places that just rely on the instuctors watch as the tech logs become horribly out of synch with reality.