So, I made the blueberry pie recipe with blackberries instead. The berries were pretty tart, so I increased the sugar to 1 C. I remembered the egg wash on the crust this time, and the lemon juice (I still left out the lemon zest, which I almost never care for).
YUM. I've never been a pie person (except for pumpkin), but this is almost enough to convert me. In any case, it's something I'll be adding to my seasonal rotation. And other times, too (since I froze enough blackberries for another two pies).
One note to emphasize in the original recipe: they weren't kidding about letting it cool down all the way before slicing it. When first cut while still warm, the filling was pretty loose and ran out into the pie plate. But left over the next day, it sliced neatly with no big oozing.