It took about 18 hours all told: 14 hours to sync the wallet and about 4 hours to update our steem transaction scanner for various changes to the steem node software (among other things, a slight change to the way transaction data is represented).
We've processed all the orders pending during this time, so if you purchased steem during the time we were down, please check your wallet and ensure that you've received your steem. All steem buy orders were processed at the price of steem at the time we received your order, so you should get it at the price you expected (not the current and likely higher price).
If you don't see your purchase, please email us at firstname.lastname@example.org with the transaction hash of your input coin. Thanks for your loyal patronage!