Thanks so much everyone. This is incredibly helpful.
More data:
The driveway is ~1200 sq ft (I didn't measure, but that's what one of the estimates says and it sounds about right).
We've already put on about $250 worth of cold patch. It seems that spending another $250 to continue to fill in the dips and to fill cracks and to seal will be $ well spent.
FWIW, we do care about the house and over the past 10 years have done a LOT of improvements, including a new roof, refinishing hardwood floors, a new garage door, re-staining the deck, upgrading kitchens and baths. I could go on. We set aside a certain amount from the rent for repairs and improvements each month. The driveway has always been on the list to repair, but it just kept getting pushed from the top as other issues needed more immediate attention. Now everything else is looking pretty good, the driveway has become the sore spot.
I don't mind paying for needed repairs, but I do hate to throw a lot of money on a repair that won't hold up and won't help resale. If another couple hundred (and a bit of work) will hold it until spring and won't turn off potential buyers, that seems like the best option.