The ping depends a lot on the distance to the host. I think if you're in the eastern or central US/Canada timezones (and have a decent connection yourself), you can expect around 100ms or less on my games. It may be more like 130 or so for west coast people, and 150-250 from Europe, again depending on exactly where you are and what your connection is like.
I will probably be getting a better connection soon, which may improve pings for those of you who are further out.
The actual amount of lag you feel also depends on the mission and number of players. BOE type missions with lots of ships and weapons flying around along with the full 12 players will give a lot more lag than a 4 player gauntlet.
If activity really picks up sharply, it may make more sense to have multiple games running from different locations (that was the original idea when this weekly multiplayer concept came up), but right now we don't really have that many players to justify splitting up.