Experience counts...
I find that personal experience is, as others have said, the only guaranteed way to form an accurate impression. However, if we go back to the days when there were no review boards, we'd all be feeling our way in the dark and kissing a lot of frogs along the way.
We all know that there are some providers in this hobby that make their money by posting enticing ads and providing poor service. They don't much repeat business but they get many first-time customers who leave some of their money behind after a bad experience.
Without review boards, we would each learn about many bait-and-switch operations the old fashioned way; that is, by wasting our time ands our money.
I have found that the best way to benefit from the reviews is to mix the knowledge posted on this board with the personal knowledge gained from the hobby. It did not take long to find other members who have reviewed some of the same SPs and who have an opinion similar to mine. Once I identified other TERBites with whom I share some common tastes, I was able to read some other reviews of theirs (of women I had not yet met) and use this information to guide my future hobbying.
While I have not had 100% satisfaction with every encounter, I certainly know that my success and satisfaction rate is much higher since I discovered review boards (and TERB in particular).
The is no such thing as complete credibility and, as always, YMMV. Still, if used wisely, the review boards can be an excellent and helpful tool.
Zog.