Increasingly, employers use automated retirement plan features to boost employee participation. It's effective. Before automatic enrollment, only 30 percent to 40 percent took part, but with it, that number soared to 90 percent to 95 percent. And everybody's happy. Or are they?

Patti Balthazor Björk, director of retirement research at Aon Hewitt, says that with less than 10 percent of employees opting out of auto enrollment, and 76 percent of employers offering target date funds that provide better equity exposure—more than 85 percent will do so by the end of the year—employees "like it.… Are people getting what they need? I think they are."

Still, she says, people must be educated to increase their contribution rate, which in most plans is initially set low.