I had a great experience selling to Matt. When I contacted him about selling my Transformers collection, he very quickly looked over the photos and descriptions I sent and responded with a quote (which seemed like a good price based on pricing information I'd seen on his site and on ebay) and followed up with detailed information about options for proceeding. After I sent the collection his way he confirmed the quote and rechecked whether he had the right paypal address to avoid any payment mix-ups. He was very friendly and responsive throughout the whole process, which was great because it was my first time selling collectables. Highly recommended!
The Transformerland site itself is a phenomenal source of information, whether or not you're planning to buy or sell there.