I certainly share the cynicism, but I've been following Bernie for sometime now, and he's consistently taken progressive positions on the issues. I'm convinced he is not pretending to be a Roosevelt democrat while intending to serve the interests of the ruling class once elected, like Presidents Obama and Clinton.
That's not Bernie. In fact I think Bernie is calling Americans to what he has referred to as "the people's political revolution." I think Bernie thought long and hard about running before he decided that he could be the catalyst for unifying progressives, while finding common cause with people across all political, social and economic lines, who believe that our country has been hijacked by a system that has brought us to a dead end.
It's happened before: maybe this time enough people will be convinced their vote would actually make some kind of difference for them and for what they care about, maybe social justice, equality, opportunity, peace instead of perpetual war, real health care for all, fewer prisons and more jobs, better schools, affordable higher education, a less corrupt politics, a healthier environment, and so on, and Bernie thinks he can be the identifiable difference maker, so we the people will have a chance to show up out and prove that democracy can work. In the end, perhaps Bernie thought he'd at least be able to say he gave us a chance to take back our country.
It feels good to me. After all, when you scratch the surface of a cynic you usually find an idealist. Why else would we care?