Avantages
I worked with Trefis as a UX consultant.
Inconvénients
I was engaged to design some revisions to the Trefis product. The founder asked me to concentrate on a particular section of the tool; we had a pleasant conversation, and then I took a bit of time to generate some new designs. When I showed the designs to the founder, he became very upset, and demanded to know why I hadn't worked on a section of the tools we hadn't discussed, in order to impress him (?!). I declined further work.
I know others in the design community in Boston who have done work for this company. Their experience is similar to mine. Avoid!