My experience with Blue Mantis was extremely frustrating. Their initial design was good. They were also willing to make edits to the design which was helpful. The reason they have receive a low rating is because of the difficulty in communication with them.
Blue Mantis does not have strong communication and understanding skills. They were unable to make basic design changes. I believe this is a reflection of their understanding and not their design skills.
I did not receive a design I was happy with and I would not recommend using this designer. This experience was frustrating and unfruitful. It definitely turned me away from 99designs.