Nothing wrong with posting negative comment about your experience. We all can have bad experience and it's useful to share it with others so that they can take that into consideration when deciding where to take their car next time.
SteelGreyDream, I appreciate you trying to share your positive experience which is also very useful for people to know. But blaming someone of immature behavior because he posted his opinion is a bit over the top.
What I am getting out of this is that what matters the most is my personal experience. We are all different and reading about experiences of others can be helpful but will not substitute our own...