I have to add my experience...
I only buy pins that I really like. I don't care if they are limited edition, or first release....I buy what I love.
With that said, DH and I went to DTD on our last day on Tuesday. I saw the pin traders set up outside the pin trading station. I had left all my pins, which were nothing special anyway, in my checked luggage so had nothing with me.
The "pro" pin traders kind of intimidate me, so I was only looking at their boards for fun. However, I did spot 2 pins that I really wanted. I love Lady & the Tramp, and always sing the Siamese song. Well, I spotted the hidden mickey Si & Am pins. I mentioned them to my husband. He said we would ask the woman (kind of young, 40's maybe, with shortish blond curly hair) what she would want for them. I told him to forget it, because I thought "those people are crazy!"
Well, when I wandered away, DH did ask, and she pointed out 2 pins on the racks she would trade for. He just bought the other two pins, and traded for the pins I wanted. She was very nice and we actually wound up trading for about 10 pins with her. Granted, she had many pins in books and wrapped, that apparently were only very special trades, but she had 4 cork boards which she freely traded for anything.
So, I did have a good experience with my "pro" trader, but can say I did overhear and see some very poor behavior from some traders. Including an argument over some "fake" pins being traded. Scary!