Many thanks to everyone who has been helping us load test RS2 over the last few days. This testing has helped me discover that it was in fact lagging more than it should do, particularly when large numbers of players were on a world at once.
I am pleased to announce I have just fixed that problem, which should make RS2 significantly less laggy. It should now be able to handle far far more players before it starts slowing down.
Also the code which sends the new game files to you when the game is updated has been improved. So updates should now download much more quickly too.