At the end of the day, I had two convincing wins and one resounding defeat. I ended up coming in 6th out of 17, which is the best I've ever done. In addition, the Dark Eldar player who tabled me went on to win the tournament. I can't feel too bad about that loss.
My Executioners won the award for Best Painted army, which was really pleasing. There were several other well-painted armies there, and I take it as a great compliment that my army was chosen. I'm not sure how I'll try to top myself next year.
Lessons Learned from the Whole Experience:
1) The Marine infantry horde definitely works. The amount of bolter fire they produce, especially at short range, is enough to give any enemy pause. The army is pretty durable, though it does get worn down against armies with good anti-infantry firepower. It's main weakness as I see it is speed. The army is really slow, so I have to plan how to reach the objectives from the beginning and make sure not to deviate from that plan. It also has to be deployed tightly so that squads don't become isolated.
2) While it's all the rage to take as much torrent firepower as possible, I really appreciated having lascannons on the Predators. They gave me the ability to pick off the Helbrutes before they could reach combat and to down the Venoms before they could do too much damage. My Dark Eldar opponent even mentioned that he rarely loses any Venoms, and he was surprised I was able to destroy 3 on the first turn.
3) Sternguard really come into their own when my entire battle plan is to pepper the enemy with as much bolter fire as possible. I generally deployed them just behind my Tactical squads. If the Tacticals are in range, then the Sternguard are also within range with their 30" range rounds. They can switch to more damaging ammo as the enemy closes. It's probably because I played two Eldar armies, but I also constantly found myself using the rounds that ignore cover. Over the course of the day, all four types of ammunition came in very handy.
4) Lysander was a serviceable HQ, absorbing tons of damage and taking out enemy characters as required (except for his embarrassing death against the Khorne Lord). That said, this list requires much less aggressive play than I was using before. I think that's why it worked so much better. With a more defensive list, less durable HQs become a possibility. Kantor would provide some assault ability (though not as much as Lysander) while making my Sternguard scoring and adding an orbital bombardment. A standard Librarian saves quite a few points and would give me some mobility with Gate of Infinity. Null Zone certainly couldn't hurt, and the Combat Tactics would have been quite nice to have to pull enemy assault units out of close-combat so they can be gunned down at short-range.