Same thing we burn 90% of the time, cottonwood. That's the only thing we have in abundance here. I have a stash of apple, walnut, mulberry and elm I'll use later in the winter for "overnighters".
We both work, so I start the fire about 4:30 in the afternoon and by 8:00 it will be 75 in the house. Our main heat is radiant hot water in the floor, but in our old drafty farmhouse it will be 65 in the house when I get home, and also in the morning.
This Sunday's high is forecast to be around 30, so I'll have a fire going all day and into the night. Might put a few chunks of apple on at bedtime.