Nope, bitcoin still has the off-by-1, as for now it's deemed "too big to fail" and fixing it would mean a backwards-incompatible change to the blockchain.
First: sorry for conflating the off-by-1 and the asymmetric adjustment issues. As I said, I haven't taken the time to consider changing the bitcoin difficulty adjustment algorithm (too big a change for too little benefit, in my opinion; if we lose 90% of hashing power in a month then there that is a sign something much more serious is wrong with bitcoin than the difficulty algorithm; speculation on what will happen when the block reward drops seems pointless to me, I don't think we'll know until it happens).
Second: I've written 'discourage blocks' infrastructure:
https://github.com/gavinandresen/bitcoin-git/tree/discourageblocks
(code reviews welcome)
... which should give us the ability to nudge miners to Do The Right Thing. Discouraging blocks that appear to be gaming the off-by-one bug should be enough incentive to prevent 50+% cartels from forming, without requiring a blockchain-splitting change.