I think, in order to receive Bernie Sanders' message as a positive, you have to agree with certain initial assumptions about the efficacy of socialism - if you have thought it through at all (and many people in America haven't thought through their political positions, I will cheerfully concede...and that's bipartisan. :) ), you will come to a point where you must ask: "Do I believe that the European models upon which Sanders' ideas are based is a better model?" and "Why do I believe that?" In order to accept any piece of socialism, you need to accept the core tenets of the philosophy that birthed it. Starting with the idea that government power is less dangerous than industrial power and including notions like the consumer-driven economy (it is common on the left to hear reasoning like: "If you increase minimum wages, people will have more discretionary spending room, so they will buy more things, so the economy will get better." Whereas in conservative circles, they talk about wealth creation to drive economy - creating new innovations that drive whole new markets...not just circulating money and goods around. You have to decide which of these you believe is right before you can accept Bernie Sanders' message as making sense to you.
He does hit on a point that even I agree with, though. He talks a great deal about how "bought and paid for" the political system has become. I don't believe the answer to that problem is publicly financed elections (that is an excellent way to get tyranny really...really quickly), but I am just as skeptical of large corporate power as I am of large government power, and I think some thought needs to be given to how to discourage corporations from unduly influencing the exchange of ideas (I could make the conservative case for making the government smaller so that there is less incentive for businesses to bribe said government for favors...but that's not the point of this thread). No message can succeed on any level without being built on some sort of fundamental truth. Sanders is doing better than anticipated because his message begins with the indisputable truth that we are being massively influenced by a very small group of people who control the way that our political parties think and operate.