Yes they are pretty sweet but they are not as good as Flame, Summer Royal, Princess, or Crimson seedless. However, those California grapes probably won't survive 6a winters, at least not every year.

You might want to consider Jupiter, Canadice, and Glenora my favorite hardy seedless.

They have far more flavor then a store bought grape, but sweetness is all dependent on how long you let them hang/amount of sun/weather/probably other factors (soil?water?). They also are smaller then a store bought California grown grape. They are very hardy and easily take -25F temps I get. Mine are just starting to show some purple.

I have 5 year old reliance. Chose them on catalogue hype, not always a good idea. But had never had the opportunity to taste them. But overall a good choice it would seem. I liken them to a cross between Concord and the reds in grocery stores for flavor. Quite tasty actually in my book. They have the slip skin like a concord, so possibly that is actually in their parentage.

Franktank, I am glad to hear yours are doing well for you surviving Winters. I have been covering mine here in zone 4. I think I will try one uncovered this Winter to see how it does. We have had -27 and -3o temps the last two Winter's, not counting additional wind chill factors. So might be a good test to see how an established plant endures. I'd really like to get the grape bunches higher up off the ground!