I wonder if there are good opportunities for automatic arbitrage between the Counterparty DEx, Bter and Poloniex.
It exists, I did some successful arbitrage trades but it takes time if you don't automate the process.
The best opportunites exists between BTER and Poloniex, since the DEX "buy orders" part is not automatic enough. But if there's a upward movement, you can take advantage of big blocks that stays available on the DEX.
Best practice (if you never did it) is to have around 400 XCP & 2 BTC on both exchanges and to transfer the difference overnight to rebalance. Don't buy when the spread is too low (below 1%).
I did 0.45 BTC profit in ten days 3 month ago. It works better when there is some volatility though... Now you'd be happy to make 0.02 BTC /day
It's always good if someone do it, since it'll provide liquidity and reduce spread. The best way should be to write a bot but that's clearly out of my scope !