The multiple sensors with an Ecobee will probably be great for you. You set up a schedule and each period is associated with a "comfort setting". That comfort setting sets target temperatures, if you're usually home or usually away, and which sensors you want the thermostat to take into account in that comfort setting. My "wake up" setting only takes into account the bedroom sensor. All other settings take into account the bedroom, kitchen and living room sensors. None of the settings take into account the thermostat's built in sensor.

I'll try and not measure the speed of my zwave network. It's never bothered me before, and I certainly don't want to start noticing and have to swap out all my switches.