I'm also running into some serious lag (9 days after this thread's creation).
I am new to Sins, but very technically competent. My machine is a beast, and I have a cable connection that lets me hit 1 MBit up, and 20 Mbit down. All of my computer resources while running the game are in good shape - CPU, RAM, network bandwidth, temperatures, etc. But for some reason, about 20 minutes into a game (mind you, I've only played two games so far) serious lag begins to hit. Lag spikes grind the map to a halt, and this is only on 2 players vs 2 AI!
What can I do??