At one time, Thompsons were the No. 1 table grape, raisin grape and wine grape in California. In a way, that very ubiquity became the Thompson's downfall. After so long at the top of the heap, they became generic.
In some cases, that was justified: A Thompson Seedless picked green is about as innocuous as a grape can be. But given a chance to ripen, a Thompson can become a pretty danged good piece of fruit. Choose them when they're really ripe and you'll be surprised at how floral and sophisticated their flavor can be.
How to choose: Thompsons don't start to get really delicious until the color turns golden, almost amber. Don't be discouraged if the grapes shake off their stems -- avoiding this problem (called “shatter” in the business) is part of what prompted early picking in the first place.
How to store: Keep grapes in the coldest part of the refrigerator wrapped in a perforated plastic bag that will allow excess moisture to escape.