SSH Encryption?
I made the same opservation, with iPhoneModem, the iPhone would get very hot and run down the battery rapidly, while now I use pdanet and the phone is just warm.
My explanation is that iPhoneModem uses an encrypted connection via ssh to tunnel data to the iPhone and back, so both sides have to encrypt all the traffic which is no problem for the Mac, but for the iPhone it can be demanding, maybe.
That would explain it becoming hot and of poor battery life with iPhoneModem, while with Netshare and Pdanet, communication goes non encrypted and therefore needs less processing power on both ends.
Anyway, that threat here got me aware of Pdanet, great little program, now I wish I could somehow "store" an ad-hoc network, it always goes away when I close everything on both side and to create a network, as easy as it is each time, is still not the "push that big button an boom" feeling I want from my Apple machinery
Any help on that?