I had a great experience selling some of my old Transformers. I had a couple of boxes at my parents and they gave me a call and said it was time for them to go. I did a few searches on how best to sell them online, and after reaching out to a few sites, transformerland.com responded quickly and had a well laid out process on how to sell the toys. Matt asked for a few pictures and a couple follow-up details, but then we quickly proceeded to a transaction.
Clearly it can be tough doing business via email, but we got on the phone, he was able to talk through the pieces with me and discuss condition. He then made me an offer, and arranged all the shipping and coordination. Payment was timely, the offer was more than fair, and he made the process seamless (and this is from somebody who does not regularly sell items online).
My guess would be everything would run as smooth on the buy side as it did on the sell side, but I would highly recommend doing business with transformerland.com.