@jeepinjeepin: My logic is that freshly-picked berries are better because they have naturally occurring wild yeast suited for breaking apart the sugars. I know that this is generally preferred in wine-making, for example.
@Gritsak: I noticed that Upland makes one, though unfortunately I don't think I'll be able to find it in the San Francisco Bay Area :/
@ryane: I can't imagine the acidity of blackberries to be more than the sour cherries used in krieks. But you're probably right, I would think any fruit flavor would be more pronounced in a "soft" lambic.
@SkinnyShamrock: Do you mean 1.5 lb / gallon or in total?