When I remote start the Jeep Grand Cherokee, with HVAC on "auto", the HVAC fan is full blast, until you open the door. It then downshifts the air flow to about 25%, until there is enough aux heater or engine heat to trigger a higher fan speed to get to desired temp.
Another one is if you want to make a quick stop, you can leave the car running, have the fob on you, lock the car and unlock as required.
Nice when the car isn't fully warmed up, like stopping at a community mailbox check, bank machine withdrawal, etc.
Have never used the remote start feature on the Buick. The salesman demonstrated it, but there's some trick to it -- the car stays locked while the engine runs, and then when you get in, you have to push the Start button? Not sure.