They produce highly unique technology and provide a great learning experience for engineering interns. My supervisors cared that I took away as much as I put in to the company during my time there.
Cons
Beacon Power went bankrupt in 2011, but has since recovered. If the technology can catch on and the company can continue to attract customers, they will be able to stay afloat.
Energy storage is the missing "link" for energy system generation integration, reliability, efficiency and security. The Beacon Power "kinetic energy" model is robust, repeatable and environmentally friendly.
Cons
As with all CapEx, pricey. The ancillary services model idea was brilliant; unfortunately, the excess capacity drove pricing below cost.