there are already bigger and better trading platforms and exchanges in the pipeline, in a couple of years we'll be looking back and thinking "I can't believe we ever used to trade on  a magic gathering exchange, it'll be like having fibre optic and remembering the good old 56k modem napster days.

Coinsetter certainly looks interesting
http://www.coinsetter.com/
http://blog.coinsetter.com/2013/04/09/coinsetter-to-bring-leverage-and-shorting-to-bitcoin-with-500000-funding-round/

just look at the people investing
"New York City-based bitcoin startup Coinsetter has taken its first outside investment by closing a seed round totaling $500,000. The round was led by Barry Silbert, the CEO and founder of SecondMarket, and Jimmy Furland, a successful London-based tech entrepreneur. Silbert invested in the company through his Bitcoin Opportunity Fund. Tribeca Venture Partners, a NYC-based venture capital firm, also took a leading role as the largest investor in the round. Other investors include Microsoft head of corporate strategy Charles Songhurst, Facebook product lead Ben Davenport, and bitcoin industry leader Roger Ver."