Just sold my MTGO collection to MTGOtraders. Yes they did prompt me to leave a review here, but I would have left one anyways because the transaction was so very smooth. I got a quote back promptly, and the quote was much better than the four other vendors I approached. It was a large collection, but there was no difficulties with receiving the payment (I chose PayPal) or transferring the collection. I would definitely recommend these guys if you're looking to cash out of MTGO.
Thanks!