Definitely brings more sense to the 3.2b price tag.
On top of that, think of what those guys still have under the hood. Google wants to be the everything of your life. Smartphones fill a part of that but smart devices are another big chunk; and Nest was the company that is undoubtely leading a revolution on the field.
This isn't a strategic move to eventually dominate the thermostat market. This is a strategic move to eventually dominate the 'everything you need' market.
HoT only appears to have the rights to certain Honeywell products and not the thermostats:
http://www.kaz.com/kaz/honeywell/
Edit: "Honeywell" that you are referring to has a market cap of almost 70 billion:
http://finance.yahoo.com/q?s=hon&ql=1