The ability to differentiate between power on and off is not a function of Pronto or any other remote, it's an issue of (dumb) mfrs not providing such a code set to begin with. Some mfrs have the codes in their library but do not publish them not provide them on their remotes (dumb). The good news is that mfrs are starting to listen more to the custom installation community and are starting to therefore provide for "explicit on" and "explicit off" commands in their libraries and on their remotes (Marantz being one such mfr, and there are others)...Perhaps Meridian has the best idea, select a source and the unit turns on, then just select off and the unit turns off. At present, as posted elswhere, the only way I know of to provide absolute power control is via the SmartLinc Houselinc system using probes which monitor state (via RF, low vdc, Hi vdc, or sync pulses). Then the Houselinc executes the macro that has been stored. We use this in combination with Pronto and it works flawlessly.
With respect to the same (dumb) mfrs that strayed into proprietary IR land for a time, they again took excessive heat from the custom install community for doing so and in most cases have come back down to reality. Let's hope that they stay here. The reality is that mfrs somehow believe that having a proprietary IR code scheme will somehow endear(force) people to buy only from them....a bit like PS2/MicroChannel I should think and we know how great that was.