Well, I haven't had a problem with multiplayer. Lag hasn't been a real issue, but I have broadband and most of the people i've played with do as well.
Most games are password protected, especially right now, because it pauses the game when someone joins. And if someone joins and just sits there deciding what character they want to play, where they want to start, etc. it gets frustrating. Even before the game was released there were a LOT of people joining any open game and then leaving once they found out more info about it - so while I was playing a game I hosted, I had like 6 people join, wait, and leave within about 15 minutes. Which took about 10 minutes worth of 'paused' time... Password protected game should go down once people become a little more understanding of pausing someone's game when you join.
The best bet is to host an open game, play for awhile, and see who sticks with you. If you find some good players you enjoy playing with, then tell them what the room name and password will be in the future so you can continue to get together with a group you're prequalified

I've met some great people off hosting open games, but 9 times out of 10, they're idiots. Especially people that join and complain constantly.
TW