I too have a whole house Insteon system and pretty much concur with your wins/losses 100% with the following additions:
-- A huge win is that outsiders need not know that the lighting is automated at all. Just use the light switch. Works pretty much like any other lighting system. In places with an 8 or 6 button switch is is still fairly obvious what button to hit to turn on the lights.
-- One button for all the kitchen lights.
-- One button for the whole main floor.
-- With my ISY994 the system smartly controls my irrigation system. It waters only when needed and avoids windy days and days with expected rain.
-- I can turn off all the lights in the house and tell the thermostat to go into setback mode with one button. I have that button programmed in the bedroom, by the front and back doors, and garage door. (programmed it to require three taps to prevent visitors from accidentally turning off the lights)
-- I have my thermostat setback when I leave the house.
-- I have my thermostat smartly look at the outside temp and adjust temperatures accordingly. Ie. it goes into setback mode if the outside temp is at all pleasant.
-- I have one button to turn on "Welcome home" mode when I enter the house.
-- I have timers to auto turn off the kids lights at night.
-- It is tied into my XBMC system and dims the lights when the movie playback starts.
-- The lights are set to come on in the case of a fire alarm trigger. (Hope I never need this).
-- Very, very rarely (a couple times a year) there is some button press on my 6 button switches which turn on every light in the house. It is easy to turn everything back off with my all-off button but it still is weird.
-- Programming is a pain but I very very rarely change anything anymore. It just works.
-- Occasionally a program stops working right but a simple ISY reboot fixes it.