Just ask Horne, who dedicated his entire career to a single employer. "Kids coming out of school have no work ethic," he says. "They think life is a video game and that you get paid because you show up."

John Martin, a 62-year-old iBank quality assurance specialist, is more tactful. "My approach to working is much different than that of today's millennials," he says. "A great number of them think there are unlimited jobs out there, and so they approach work a little more casually than people of my generation."

Defining 'Professional'

It's this perception among boomers that deeply offends Nathan Williams, a 30-year-old Serena software engineer who identifies with the millennial generation. "There's the misconception that we're just not professional. But the truth is, we have different ideas of what it means to be professional, and a casual attitude is part of that."

In fact, Williams says millennials' easygoing disposition encourages creativity and "a willingness to break boundaries" that contributes to tasks such as product development.