The World of Warcraft community site has been updated with a fairly lengthy list of changes made to several classes and specs with specific regard to PvP. Many of the affected classes have had base stats tweaked to better balance the game. For instance, while Frost Death Knights have had Strength reduced by 10%, Warriors have had Strength and Stamina boosted by 10%. In addition to PvP updates, smaller fixes have been applied to class halls, dungeons & raids, and items.
PvP has been a divisive topic on the World of Warcraft community forum with many players finding blanket adjustments to base stats an ineffective way to balance PvP. You can check out the NA forum to see what is being said about today's update.
Read the full hotfix notes on the World of Warcraft site.