i think 5-star reviews should always be taken with a grain of salt. negative reviews, on the other hand, should be taken quite seriously. i think few people will post a negative review if the bad experience wasn't there to back it up.
i have definitely had the experience of a subpar session with a provider who has numerous five-star reviews. i think that comes with the territory when we play in this playground. there will simply be providers that don't work for us as well as they might for others. i have never left a less-than-5-star review for a provider, as i am not out to ruin anyone's livelihood. if i do not enjoy the experience, i will not rate them at all. hypothetically, the only time i might post a negative review is if i felt the whole thing was a scam of some kind, but (fortunately) i have never had that experience.