Got back from my local M12 prerelease event (day 1) about an hour ago. I was there for about 10 hours. 100 people showed up for the tournament, packed into a gaming shop about the size of your average McDonalds with the kitchen. So I'm now a card-carrying member of the DCI.
It was a 6-booster sealed deck thing, where you opened up all your boosters and then passed the lot of cards over a few spots. I passed a set that was heavy black-red, and got one that was about equally balanced in number. The store ran out of plains really early, and after nearly everyone set up they were out of islands, too. I set up a R/B deck centered around bloodthirst creatures and discard.
Round 1: A 2-1 loss to a R/B/U flying/control deck. At that point I had only one flyer in the deck, so I swapped out some discard and added green.
Round 2: A 2-0 loss to a B/W vampire/aura deck, though both matches were really close.
Round 3: A 2-1 loss to a R/B Goblin/bloodthirst deck. Again, somewhat close for both.
Round 4: A 2-0 loss to a W/B deck. This was the single worst round I had, in which I was proud to actually hit the guy once each match.
Round 5: A 2-0 win to a U/W flying/control deck. I managed to get my bloodthirst creatures out the gate before he could lay down defenses in the first match, and I got to set up my sole uber-combo (see below) in the second.
Round 6: A 2-1 loss to a W/G deathtouch/flying deck. Nothing particularly notable.
Round 7: A 2-1 loss to a U/G creature deck. I got mana screwed in both the losses, and won the other with a last-play Naturalize.
Top 5 Cards as far as use went:
1/2: Royal Assassin / Crown of Empires: When I got both of these out, I tended to win.
3: Goblin Fireslinger: The Goblin Tim probably did the most damage out of all the creatures I had over the course of the day.
4: Volcanic Dragon: My top flyer, great defender.
5: Incinerate: I guess, in that it was the final damage for two wins and burned down a crucial defender for a third.
So all in all I finished 1-6, 79th out of 100 and second-last among people who stayed through the whole thing. I met all four of my "realistic" goals (win a match, don't finish last, have fun, get at least one card I didn't have from an older set), and 2 out of 5 of my "dream" goals (win a round, not get shut out in damage in any match - though it was close; I didn't get "win something" - someone got $250 in a random draw, and when I left they were starting the top 16; didn't get "finish in the top half"; didn't get "get a Planeswalker").