The big value is not having to completely trust the person holding the money. As of right now if you do escrow you transfer money to a third party, who has the option of taking it and running.

With a correctly setup transaction, bitcoins can be held in escrow that require 2 of 3 people to approve moving it. This means that you/seller, you/escrow, or seller/escrow are the only 3 combos to get the bitcoins out. There's no way for the escrow agent to steal the money.