I used fiverr a lot of times, tried different sellers/gigs and had both positive and negative experiences
Positive. A lot of sellers, various and very interesting gigs, cheap cost - 5 bucks for everything. And easy to cancel the order if seller failed to deliver on time
Negative. A huge number of scam sellers. My examples, I bought 500 twitter subscribers from US but got only 200, mainly bots and part not from America. Or translation, seller sent me german translation of my article and i'm pretty sure he used Google or something. But no chances to prove something to Customer support