I've been twice and I gave up after 2 days both times. CM refusing trades and only willing to trade LEs for LEs put me off of trading. I actually had decent luck trading with guests in 2004 but I only was one sharkish type guy in 2010 with about 8 pin books spread out. I flipped through his books a bit but it was almost all LEs and CM pins so I didn't even bother to try to make a trade.
There is one place where you can indeed only trade LE for LE, but that is at the pin board that comes out at Harringtons some times and at board at the Pueblo Trading Posts.
I've actually had a CM refusing an LE of mine saying they couldn't trade for a rack pin. Others insist you need to "trade for a pin of the same size" or are refusing to trade because it's their "personal pin."