I just made a purchase of two coins from a reputable dealer - part of the price negotiation involved the Dealer asking me to use Transferwise in order to meet my number.. I have had excellent experiences with this Dealer in the past so have no issue with trust. Wasn't too difficult to set up. This was an expensive purchase (by my standards) so I am paying over a few installments. First installment went through successfully and was much cheaper than PayPal. So far so good.. but as usual won't relax until the coins are in hand.
I have used Transferwise for payments to the US and to Ukraine (where PayPal doesn't work). The costs of the transfer were about a quarter of the normal bank fees, plus I got a good Exchange rate. Everything went extremely smoothly.