Bittrex's blockchain has synched.
So are deposits and withdrawals working on all exchanges again? Is Bittrex and Poloniex running 0.9.1?
Bittrex just sent with mixing lev 0,
so i would say they have not updated. But if I were an exchange I would not update until I was sure there were no bugs in the latest release. Usually a week is a good timeframe to gauge whether there is a glaring error.
You will notice that corporations tend to stay with versions they know are stable and do not beta test ever. This is sound practice when money is involved. For all you youngins, there used to be an industry for nothing but beta testing where people actually were paid to make sure a product was ready for the end user. The level of professionalism in this industry is creeping to the lowest common denominator (I.E. M$). And I blame the fools that put up with it for it.
/rant off
That doesn't necessarily has to be the case. Bear in mind that the default of simplewallet is mixin = 4, but you can still make mixin = 0 transactions via the RPC API, which exchanges probably use. However, for all we know they are still in 0.8.8.6. Anyway, after 20 March mixin = 3 will be enforced.