I have been told several times that what really makes or breaks you at a PT is your support structure. Having a team that you can test with and run a gauntlet of common match ups is invaluable. You can get away with 3 or 4 games before a FNM with a tier 1 deck and probably know enough about it to do reasonably well. That's not at all the case with a big tournament though.
Also, aren't most PTs combined constructed & sealed? That's what keeps me from trying that much. My sealed game is just terrible. It's a completely different set of skills that I just never developed and frankly don't enjoy as much. Very surprised to hear that Grand Prix are more competitive than PTQs, though. That seems counter intuitive, since Grand Prix are supposed to work as feeder events.
In other news, we're having our first Modern tourney this Saturday at my local shop. They're less than a year old, and FNM is topping 50 players regularly now so it's really great to see some competition. With MM releasing, enough people are now interested in the format that they're going to start expanding. I'm liking Modern more and more; it reminds me of the old days of MTG.
Assuming TCG doesn't fuck me, I should have a pretty damn competitive Melira Pod deck for this weekend. I've got to skimp on fetches for a bit (6 instead of 4, using Marsh Flats instead of Misty Rainforests), but I should be fine for our first tourney. I don't think decks will be too highly optimized just yet.