I heard about this yesterday on the radio as I was heading home. I'm not the least bit surprised that researchers have found that brain exercising software doesn't actually benefit cognition.
Why am I not surprised? Because these programs were written for a broad base of people and had absolutely no scientific approach as to how or why they might help cognition (more pop-science). They were written as entertainment being sold as science, much like most of the "health" supplements you see on the market. It's not necessarily harmful and it makes people feel better.