Tweaks to net code went live at 2am PST this morning for Xbox (PS3 to follow shortly if no ill effects occur). This should improve the situation for those hosting sessions. People experiencing host disadvantage please report in if this has influenced your experience. Re-launch of the MP game is necessary to receive the settings if your Xbox has been left on since this time.
It will, therefore, take a time to propagate this change to all Xbox players. Those with ISPs with good upload speed please desist from lag switching/downloading torrents/bandwidth throttling while this tweak is tested.
I assume this is the .2 hotfix.