My LGS did a free Frontier tourney a few weeks back. They have out a lot of promo cards to everyone that came; it was kinda neat.
The format itself was dominated by jeskai aggro control. I took a UG ramp deck that finished 8th overall (out of 30 some) but lost to the guy that ended up winning it twice.
Declaration in Stone was probably the most played card, at least against me. Abzan had a few representatives, but they only fared moderately well. I only saw one mono red aggro deck, and while he finished well (5th?) he struggled at times to get rolling.
I can see that format taking off pretty well, especially if they get a banned list going. I used
Treasure Cruise to great effect quite a bit and I heard a few other people running
Dig Through Time, but never had to face them. Didn't actually see a Co-Co deck, surprisingly.