How Much Do Reviews Reflect Real Experiences?

I’ve been comparing different online services lately, and I usually like to read several customer experiences before forming an opinion. Reviews can be helpful because they highlight both positive and negative experiences that may not be obvious from a service’s website. I recently came across Reviews for By Pass My Exam while doing some research and found it interesting to see how people use reviews when making decisions.
How much do you rely on customer reviews when choosing an online service?