I am now partial to StubHub.
As a buyer, I never experienced any issues purchasing concert or sporting event tickets. I was cautious when choosing my ticket purchases as well, however. In one instance, the seller listed the basketball tickets I purchased as "instant download" but in fact they were real tickets. StubHub identified and intervened and had the seller UPS overnight the tickets to me. So, as a buyer, I have not experienced any issues.
As a seller, I now can paint a different picture. I just sold my first set of NCAA basketball tickets. I listed them yesterday and they sold today, but $10 less per ticket than the price I listed them for. I immediately contacted StubHub customer service, they implied it could be a system error or it could be a seller error. I immediately replied that I have an email confirmation, i. E. proof, of the ticket price I listed them for. A few minutes later, the agent said StubHub will issue me payment for the difference but will take 2 to 3 business days. I just cleared this up today, and so I can not comment on whether StubHub has lived up to their commitment of issuing me funds for their screw-up...