@Zan Lynx: It absolutely did take a number of versions before a good network protocol was determined. I just wanted to point out that using UDP isn't a bad thing, in the end it will always depend on many factors related to the game/environment.

@Zan Lynx, Using TCP over a poor connection is even worse than UDP. With UDP you can create an algorithm to handle dropped packets via interpolation, delays, etc (look at Source Multiplayer Networking). TCP over a poor connection means the whole game will stall repeatedly while lost packets are resent, which will happen very often on a poor connection. TCP is good for solid connections with enough bandwidth to support the data load (example: LAN, Broadband). UDP with a bit of extra work will always perform on bad connections. This was done with Doom/Quake and many other older games.