How easy would it be to implement this in BitShares? TLDR; Payments are locked for nBlocks and refunded unless a secret from receiver is revealed.

https://bitcointalk.org/index.php?topic=628547.0
http://upcoder.com/11/atomic-cross-chain-exchange/

I would love to be able to trade BitUSD for Bitcoin or other alts directly and not have to deal with going though BTS everytime.

Firstly, let me start by saying congrats on the BitSharesX going live.. i've been playing around with it and its working well.

I just wanted to share my thoughts on the platform, its positives and negatives..

I love the idea of a decentralized BitUSD, its the only way to get around the obstacles that centralized exchanges were facing dealing with fiat currencies and there associated regulations.

I also believe the market will keep the price of BitUSD where it should be (although the first major short squeeze will be fun to watch).

Now this is not really a problem, more of an observation, if we can create BitUSD out of thin air using BTSX as collateral and start trading it, how do we determine the price of USD/BTSX?  obviously we can check other centralized markets and use their prices.  And the good (and bad) thing with USD is there is so much of it out there, traded everywhere its nearly impossible to determine an accurate price so we just go with what the big boys tell us.

But what if we wanted to create an BitAsset based on an asset that did have limited supply and demand, and had illiquid markets.. the BitShares "virtual" version would never be able to take over as the leading marketplace or primary point for determining price because no one is actually swapping the real asset.

So my conclusion is USD/BTSX is probably the best market for BitShares because we just accept the price the big boys tell us.. but BitShares can never become the primary exchange for Bitcoin, potentially even Gold due to it not being able to determine its own real price.  It can only be a small percentage of the real markets that actually demand swapping/depositing of the real asset.
Saying that, even if BitShares fulfills only a small percentage of trading for a given asset, maybe that's enough to facilitate a virtual representation of said real asset enough that they can be transferred around on a blockchain p2p style with no restrictions or red tape

TLDR; Without supply and demand of actual assets there can be no independent price discovery.