Tried a deck very similar to this last week. Learned that due to the new fetchlands you need to decide between Red or Black as your primary color and then white as the secondary and then either red or black as the tertiary color. You'll have problems drawing white mana otherwise.Check out my deck Mongolian Super Buffet

+1 from me fellow Mardu clansmen. Mardu and aggro is the way to go! Deck is well structured with a good CMC average that should keep things moving along smoothly. My only recommendation would be to consider adding Utter End into the sideboard for situations where an artifact or an enchantment is proving to be problematic. Other than that it looks very aggressive, which is my kinda style. I too have a mardu deck, the Butcher of Mardu, and if you get the chance I'd like to hear your opinion. Great deck, and let me know how the sideboard construction comes along.