I'd ask for hashproof before bidding on someone hesitant of escrow.
just redirect mining to your eligius address for 3 minutes..
even with that it just proves that he has some hashing power....what is the guarantee that it will be shipped?
Look at our discussion from pro-miners.net here (
https://bitcointalk.org/index.php?topic=279406.msg2990647#msg2990647)