The thing that is still hurting Birmingham is it's image as a dangerous city of crime. That said, it is partly true because there are some downright dangerous neighborhoods just north of downtown, hell, all around the city, and some of it has spilled into the CBD.
Another thing is that overall, the City of Birmingham is still an industrial city, and most of the office development is occuring in The Summit area in the far SE side of the city. The other area of growing office space is Hoover, especially aroung the Riverchase Galleria.