Those logging in today will be greeted with the Blizzard Downloader as the small 2.1.3 patch went live, fixing some bugs and changing a few game elements:

General
- Read in-game mail will now be kept for thirty days instead of three.
- The Warlock spell Incinerate has had the performance of its graphical spell effect improved.
- The "Show Launcher" option has changed so that it now defaults to "on". Players will now see the launcher when running WoW by default.

User Interface
- Improved the performance of conditional macros, slightly increasing the framerate.
- Fixed a crash triggered by many unit frame AddOns.

Bug Fixes
- Fixed an issue with the movement of Archimonde's Doomfire.
- Fixed the wand missile art on most Shadow based wands to show the correct graphical effect.
- Infinity Blades will now despawn properly when the encounter with Kael'thas resets after a wipe.
- Gan'arg Underlings and Felhound Defenders are now properly classified as demons.

Among the more important changes are the addition of more time for mail (Auction House alts around the world rejoice) and the fix to the unit frame AddOn crash, which may have been the reason for crashes following disconnects while in a raid instance.

If you're having problems connecting to Blizzard's official downloader, a File shack mirror is available now.