Even though a thermostat is one of the least expensive items that you will buy when you buy a heating and air conditioning system, it is very important because it is the interface between you and the heating and air conditioning equipment.
We would suggest that you purchase a thermostat that can be run as either a programmable or a non-programmable thermostat. The difference between the costs is very little, and you then have the option to program settings to save money when you're away from the house, etc.
In addition to losing the poisonous and polluting mercury of older thermostats, new digital thermostats are more accurate and have many features that make comfort control even easier.
Wireless thermostats are also perfect for certain situations. They can be placed anywhere in the house and control the temperature of that space.
Keep in mind that you can choose your thermostat independent of the brand of your HVAC equipment. Thermostats are designed and built to certain standards that allow interoperability across different manufacturer platforms.
More thermostat information available at Thermostats USA.