Everyone has different experiences in different things in life - wether it be a dodgy pizza or bad holiday but it's common practice for people to only leave a review if they have had a bad experience which is unfair as i'm sure if all the people who were happy left good reviews then these would far outweigh the bad ones.
What you have to remember here is, you're getting a service for peanuts compared to what you should be paying so don't expect perfection - if you want perfection then pay for a legitimate service but even then, these aren't always guaranteed to be fault free.
My advice would be to try it and if you're not happy, just move onto the next.