i'd never buy or sell anything on 50% escrow.
You clearly state the terms, then the escrow will abide by it..
I made a sale once, and buyer didnt make note of receiving the item. but the goods were signed off.
I just had a part of the term, being 6 hours after signed receipt, escrow is released.. so he cannot sit on it forever..
In the end, he confirmed all ok, but after 24hours.
Escrows (in this case i always use SebastianJu as he is free/donation), always are trusted. there is no gain for them to screw the deal. Yes they could run with the btc, but i believe they make more by getting the donations than getting a oneoff..