I suffer from the same syndrome of buying things at the end of the season when they are on sale.

I often just plant them temporarily in the pot and move them in the spring. Bury the pot to the rim with an inch of pot or so showing, water the pot and surrounding area to make contact between the drain holes and the soil. Cover with mulch. Water ocassionally if the winter is dry. That way you can spend the winter finding the ideal pot or the ideal spot.

The only plant I had that didn't make it was a dwarf pomegranite that was only marginally hardy in this region.

What about the burlap wrapped around the base? Do you take that off?

Not sure where you live but you may have to protect the small branches from the cold. I have a small coral bark that I bought a number of years ago. First the deer took care of the main branch. The tree kept coming back but every winter the small branches would die in the cold. Every spring and summer the plant would start growing new branches. The tree is a wimpy 18" high. I think I'll try to protect it this year and see what happens.
Does anyone know if this happens with larger branches? I like the tree and may just buy a larger one.

Dig a hole and plant the pot as is. Take it out and take the burlap off in the spring if you want to, and then plant it in it's permanent place. Lots of people plant balled and burlapped trees with the burlap still on, just remove any wires if there are any around the tree when you plant it in a permanent place in the spring. Plant it temporarily in a place where it will be protected from winds this winter. For example, the east side of our house is good because the wind mostly comes from the west. Mulch it heavily with dry leaves around the base of the tree and up around the trunk. You might get a little tip die-back, but the tree should store well this way.