Re: extract, I think it is an OK supplement, but not good for the whole flavor (following HoosierBrew's philosophy). E.g., if you do a raspberry beer, use frozen or canned raspberries, and then add a tiny bit of extract at kegging/bottling *only if needed for flavor/aroma*. You want just a hint; too much extract, and it will start tasting medicinal.
Based on my own experience, I would recommend using frozen fruit (perhaps pureed in a blender) over canned purees, if possible. The canned stuff can produce a good product too, but the flavor and color will be just a touch brighter from frozen fruit. I usually add the fruit (either canned or frozen) 3 to 4 days into primary fermentation; this seems to be a good compromise between speed and preservation of flavor.