The escrow deposits sent will be kept at the same value regardless if it's in BTC or Fiat.
If you accept and pays in fiat many of us would be more interested.
My understanding is you can pay in fiat. I don't recall even seeing it discussed on the web site that paying in BTC was an option, although I assume so. My plan was to pay the escrow agent in Fiat. Xcrowd can confirm this is allowed, hopefully. (Would escrow.com even allow escrow payments in BTC?)