The (free) Delving Deeper Reference Rules PDFs have been updated on RPGNow, I've only had a chance to look briefly at the errata document, which is supposed to cover all the changes made between v1 and v2. One of the main changes is that a couple things from Chainmail have been added (not combat rules, but some descriptive things about creatures and a couple fighter bonuses.) There was an error in the first reference doc, though, where two saving throw categories are swapped in every class. Also, they seem to have tweaked the hit dice progression for M-Us and Thieves.
I haven't noticed yet if they've fixed the cleric spell progression. Probably not, because I think that was an intentional choice.
I'll have more commentary after I've had a chance to examine it.