I think the only time I tried brown malt, it was from Simpsons. HorribleAfter trying the Porter I decided to go back to Crisp's brown malt. The darker one from Simpson's just is a bit too intense.
Never touched that again.
After aging for half a year though.... Lovely! I guess it all depends....
I'm now into Imperial malt. That one tastes like I want it right from the beginning.
About 50% of the grist roughly equals 15% brown malt I would say.