I have been using an Ecobee3 Lite thermostat since 2019. Aside from the issue described in Hydro One's myEnergyRewards in Action, it has met my needs. I can create schedules that minimise furnace and A/C operation without impacting comfort levels.
Ecobee
I am probably not a suitable candidate for demand response programs. I signed up for time-of-use (TOU) billing and try to shift electricity usage into the weekday low period from 19:00 to 07:00. During the summer, the air condition mostly runs at night, cooling the house to 21C from 23:00 to 07:00.