Two good experiences

I have used viagogo twice now. I had looked at them for Monty Python tickets, but wasn't sure if I could trust this site. However, I then wanted a ticket for Roland Garros and they were the official re-sale partner. I ordered my Roland Garros ticket and that all worked out fine. All ticketing done on-line. I then decided to try my luck for the Monty Python show as well. Until we got to the door, I was still worried that the tickets might not be real, but they were. And I paid less than half price!
Of course I am lucky in that I live in Greenwich and my ticket did only arrive the day before, but I had no travel arrangements to make. I also have not had to contact anyone for refunds. But please remember, viagogo is just a portal between people looking to sell tickets and people looking to buy. They do not hold the tickets themselves and you pay what the seller wants. If you think it's too much, don't buy or try the official ticketing partner first!
My only quibble? Tickets via "signed for delivery" - a complete pain if you don't happen to be at home.