They taste like exquisitely flavored sorbets.
You should eat them immediately. They have a pleasantly crisp consistency but they do not get rock hard, probably because of the sugar content. If you leave these little beauties out for more than 15 minutes, they tend to get mushy, so put out small portions and keep refilling the plate.
Margie Ryan suggests serving them with chunks of hard cheese, but I prefer them unaccompanied.
Freezing grapes is the best solution I have found for keeping grapes tasty. Stores no longer sell little bunches any more and we find that grapes tend to get soft before we can finish them. If we buy a Food Lion bag of grapes, we are looking at a two week supply and the grapes do not last that long.
Popping most of the bag in the freezer (after washing them of course) gives us an endless supply of frosty flavor bursts with no mess and no wasted grapes.
Thanks, Margie, for the suggestion!