Good to know, I found an extract at my LHBS. they also sell canned puree. Should i assume the puree will react the same way as the fresh fruit?
IME - the canned purees (normally in the wine section) of my LHBS are fantastic. And it saves you from pureeing/sifting fresh fruit yourself.
I've done exactly one fresh blackberry beer. I spent a lot of money at the Farmers Market, got a low yield of puree, and still ended up with seeds in my beer (but not much blackberry flavor OR color).
If you want the fruit to be the main attraction, you're going to need a lot of puree - more than you think. The flavor is quite mellow. When I make fruit beer, I add it to the keg. I'll buy 4 3-lb cans of puree, add two, and then continue adding one at a time until the flavor is to my liking. With blackberry, I wouldn't be surprised to add all 12 lbs.
Just like adding lemon juice to a fruity cocktail or dessert, adding the zest of a lemon or two will punch up the fruity flavor.