Taking a long time at the moment with:
"Hang tight, we are getting the safe multisignature escrow ready so you can deposit the bitcoins."
It's slightly in favor of the person selling their coins in exchange for the goods:
"To complete it, a transaction requires actions by two independent parties: (1) the bitcoin buyer must complete the purchase on behalf of the bitcoin spender and acknowledge it; (2) the bitcoin spender must acknowledge receiving and accepting the items. When the bitcoin spender receives the items, he/she may choose to accept them or return them. If accepted, the transaction can be completed and the bitcoins will be released to the bitcoin buyer. If returned, the transaction is cancelled and the bitcoin buyer should receive a refund.
In the best-case scenario, both parties acknowledge their respective actions as soon as performed, and the total time depends on the timing of the online merchants involved.""
