I brewed the Northern Brewer BBP extract kit a few months ago ... I actually used 20oz Maker's Mark in the 5g batch -- which was added to the SECONDARY with the oak chips. It came out REALLY well. I've had many folks comment on the complexity of the flavor ... most of whom are not even big beer drinkers.
It's a brew that's getting better & better with age, and I need to start rationing the bottles from myself. Believe it or not, it's actually not at all overpowering. Kind of chocolatey... I'm probably not the best at describing tastes, other than "damn, that's good!"
I just don't understand how some folks are saying only 2-4 oz in a 5g batch. That seems it would be fairly faint (IMO)