Sorcerers still can't quicken
The new haste
No new class skills for sorcerers
The Red Wizard in the DMG
For other changes, I am waiting to see the rest of the game before I make an opinion. Sorcerers were, IMO, somewhat shafted, being balanced only when made for combat. And now that, thanks to the new haste and the old metamagic system, they can't even be effective combat machines...
The fact that their puny class skill list don't improve is also annoying. Adding diplomacy, intimidation and use magic device to them will stay a house rule of mine.
And finally, I would have liked a new setting-specific PrC, rather than a rewarmed Red Wizard. As I said in the DMG 3.5 PRC thread, a Scarlet Brother would have been nice, especially given that it would have made 4 new PrC rather than 3 (provided the horizon walker isn't the gatecrasher from the MotP, in which case we would have only 2 new PrC).