It looks like some pretty big nerfs to the Yogg-Saron fight tonight. Ulduar's big bad (well, one of two) will have a much easier first phase, as the Guardians of Yogg-Saron have ceased mind-controlling players, as well as becoming "more forgiving" in their spawn rate. Additionally, flash-frozen players that touch a cloud will no longer bring forth a Guardian.
Flame Leviathan's hard mode was hit as well. The amount of extra health he gets per tower up was reduced and the snare effect of Hodir's tower removed. Additionally, vehicles caught in a flash freeze will be freed with a single shot from a Demolisher or Siege Engine cannon. Players will also not go quite so high when ejected from Flamey following a stun, which should make them a bit easier to pick up.
Oh, and XT-002 Deconstructor won't make people into bombs quite so often (and his heart's health was reduced a touch on 25-man). Overall, it seems Yoggy will be significantly easier. My guild isn't there yet, though (next up for us is Mimiron) - people who have done the fight, how big of a deal will these changes be?