My gas furnace just died last week, and thanks to a home warranty, I got a new one installed over the weekend. My old furnace seemed to come on and off at what I thought was a fairly regular schedule, off for 15 or 20, on for 10... etc. Something like that. Being a new furnace I've been paying very close attention to how it is behaving. Yesterday morning at 6am my programmable thermo kicked things on to raise the temp to 70 degrees. The house was currently at 68 degrees. Three hours later it finally reached 70. That seems very wrong to me. And I can only imagine what that might be doing to my gas bill.

If this is a new unit I would definitely call the people who installed it and have them come back and do some troubleshooting on this.

With programmable stats, sometimes the thermostat has to LEARN the behavior of the house when it comes to programming. Many try to make the temp of the hose to be x at the programmed y time. Sometimes the adaptive algorithm can be disabled.

If your having issues with overshoot, then the CPH or Cycles Per Hour, can sometimes be reduced in the stat. This is the same as the old "anicipator" adjust.

Thermostat is the same one I had before. To add a little more to my story, my thermo is in what I consider to be a bad place, its directly on the other side of the wall from the furnace The main line that runs to all the registers runs through the floor right under the thermostat. This floor has ceramic tile and it seems to act as a conduit, being pretty warm when the furnace is running, warming up that area 3 or so degrees more than the rest of house, in turn turning the furnace off before the rest of the house was all that warm. I don't have that behavior now, which, while not necessarily a behavior I want, is telling me that air coming into the house isn't as hot as it was before.

What thermostat do you have?
Post link to manual if you can.
Can you change CPH in the stat?
What is it set too?

You also should be aware that some thermostats can have a remote sensor, so sensing takes place at a different place than the thermostat.

Problem solved. The wrong furnace was put in. They put in a 2 burner instead of a 3. Things are working great now. I'm just still in awe that they admitted it, and came out one day later and made it right.