The first official installment of patch 2.3 is now available to the Blizzard Background Downloader. While it may still be several weeks until the patch is activated on the live realms, this is nonetheless a sign of hope for many players who have been eagerly anticipating the new content. I have no doubt that the patch release date guessing game will come up at least once in guild chat while I'm online tonight. (I might even be the instigator.)
Many people I've grouped with in game have complained of extra latency while the Downloader is running. If you start to notice this problem while playing tonight, you can always alt-tab out and suspend the download. Also, you can always access the options for the Downloader through the WoW Launcher which, in turn, can be enabled/disabled from your login screen. Additionally, if you'd like to start downloading without starting up WoW, you can use the Background Downloader icon in the WoW folder on your hard drive. For further questions, be sure to check out the Blizzard support page for more help on the subject.