Once hired a 55 Baron where the airswitch was actually attached to the gear squat switch, which meant you only paid when the gear was up - very tempting to do lots of practice ILSes in that one! Even a normal airswitch is a much better (and fairer) proposition in high performance aircraft, especially if you are flying relatively short legs (where the taxi time is a bigger proportion of the total time). Plus - no incentive to rush to pre-take off checks and much less likely to get agro with ATC when they tell you to expect a 10 minute delay while on the ground at BK while SY DEP identifies and separates the VFR C152 that just departed into Class C in front of you!