Being in the center to me means to have good comprehension of the back-end, being comfortable with frameworks like Rails, having great front-end skills and on the design side having a good feel for user behaviour (UX facets).
Abstracting this, it depends where your rational comfort zone is (logic -> irrational). I have a good feel for user behaviour and can use my analytic skills on UX challenges, but also foresee and implement these on UX – dev challenges.
The biggest benefit of these center positions, is the ability to converse with both departments and to voice new insights and concepts which are often outside the scope of these departments.
Unfortunately the job market has little understanding of this profile. Department stake holders (CD or senior devs) are protective of their area and recruiters have a hard time profiling you. This might be anecdotal though, being from Europe, which is not so innovative as some areas in the US.