A decade or two ago, those that were available to the general public they were just interesting novelty plants with fruits that one would honestly consider survival food - edible if nothing else is available. The fruit was also very small.
Nowadays there are many cultivars that are normal dessert fruit in taste and they are a good size. The taste is quite near the regular wild blueberries.
For the USA / Canada folks: I'm in Europe. "Blueberry" is used for another plant here. You call ours "European blueberries" and we call yours "American blueberries". Here, catch -
Anyway, the good cultivars that I can vouch for are the Boreal series: Boreal beauty, Boreal blizzard, Boreal beast. I'm told that Aurora, Strawberry sensation etc. are also great but haven't tried them, we grow close to 30 Boreals and it's enough for a family orchard.
In our experience Boreal beauty is the most practical because it's easier to pick than the others - it doesn't squish as easily while being harvested. Blizzard tends to be a little sweeter though.
Possibly important for you as you're in Greece: haskaps tend to become shriveled and dry when summer starts regardless of how much you water them, they just shut down because of the heat. But this is in our experience much less pronounced in the Boreal cultivars so that's also a plus.
thank you!