Halo 2 will allow four people to connect to Xbox Live on the same Xbox at the same time. That's just one of many closely guarded details that a cheeky beta tester announced to Microsoft's Xbox.com forums last week before his posts were summarily deleted by moderators.
Fortunately, some bright spark mirrored the details on the Gaming-Age forums, where you can now read them in their entirety. Typically, Microsoft has issued the usual refusal to comment on "rumour or speculation" regarding the leak, but at this stage there's no reason to think it's anything other than genuine. In other words, it's not quite gospel, but it's definitely from the church of Halo.
Key points, then, for those who can't be bothered to take in the whole thing: there are three maps in the Halo 2 multiplayer beta currently undergoing testing (E3 map Zanzibar, Covenant battleship-based Mid Ship, and the elevator and air vent-heavy Ivory Tower); dual wield SMGs are lethal; there are new Covenant weapons like sniper rifle equivalent Beam Rifle and the Brute Shot, which packs a wallop like a shotgun; you can jump higher but move a bit slower whilst holding the bomb or a flag; and there are multiple melee attacks per weapon.
The author also compares the difficulty and adrenaline rush of a successful vehicle-hijack move to killing someone with a knife in Counter-Strike, which is bound to speak volumes to most of you. A bit like juvenile shoplifting then. (Maybe they could put that on the box?)
For more details we'd encourage you to read the whole thread. Just remember: Microsoft hasn't confirmed these details, and it hasn't denied them either. What it has done though is delete them from its own forum, which is probably as close to confirmation as we'll have before Halo 2 ships in Europe on November 11th.