I have an Ecobee3 here’s my opinion.
Like previously stated you can control temperature of the WHOLE house using various sensors. The thermostat can be configured to average which sensors you want and which to use in each mode.
If you want to direct more or less air to different vents. Then you need to look into Keen vents option.
If you want more control and more options when using your Ecobee3 rhen you should look at @yvesracine DTH and Smart Apps. They can utilize Keen vents, and help control the thermostat using various inputs. I highly recommend it! I have been using it from the day I got my thermostat.
Here is a discussion about his latest version:
It will serve as a good starting point to get you more information and link’s to his software. He is very helpful and will answer any questions you might have in the various discussions of his software.
Hope that helps.