There's a lot of Magic being played out there. With a Grand Prix of this size it's hard to distill the essence of the Day 1 metagame. I took a quick tour around the top forty or so tables to get a very unscientific breakdown of what the undefeateds are playing.
Perhaps the biggest surprise for me is that Mono-Blue Devotion decks are out in force. They were far and away the most numerous with around ten players pinning their hopes on Master of Waves. Next there were three archetypes with about seven or eight players apiece: The Black-White goodstuff deck that evolved out of Mono-Black Control, Esper Control decks (surprisingly outshining straight Blue-White), and base-red Aggro decks, both the all-in on Bolts version and the more straightforward creature-based strategies.
I saw a few people playing Green-Red Devotion decks reminiscent of Makihito Mihara's Pro Tour deck. There were also a few bold souls sporting Bant colors for their Control shell. Lastly there were a smattering of White Weenie, Mono-Black Devotion, and Blue-White Control. For such a diverse field there were few real rogue decks. Although, and I don't want to say too much here, I did see a Spellheart Chimera in play.