Let's face it though. He is guilty. He admits what he's done. We can argue about what the law should be, but not what the law is. It's illegal to take classified documents like Snowden did, and start giving them away to everybody like Snowden did. His reasons for doing what he did are irrelevant as it pertains to his legal liability. The fact that he or even the public sees himself as a whistle blower over illegal actions by the government are irrelevant as they pertain to his legal liability.
Of course, we do have jury nullification in the common law system. A jury could very well say, okay, well he did the crime, the evidence is overwhelming, but we're not going to say he's guilty because we don't agree with the law. That's quite possible. Sure, the prosecutor and judge will try to tell the jury that's not allowed, but it is, and it can happen. The jury system exists specifically so the people can check the government's power.
This is all a separate matter from trial fairness, of course. If I was Snowden, I might not be so inclined to trust a US federal court with my fate. The judge might disallow evidence or testimony that would give Snowden and his lawyers a chance to argue however subtlety for jury nullification. The judge might not sustain valid objections from the defense. The judge could give a horribly unfair instruction. All kinds of things could happen. Considering the overwhelming political pressures that are sure to be placed on any kind of trial, Snowden might very well find himself screwed. He might also think it was all worth it anyway.
Then of course we have the appeals system and of course the presidential pardon. Even if Snowden doesn't get a jury to nullify, that's hardly the end of it. He might get his case to the Supreme Court and have a fairer chance there. He might also have a groundswell of popular support that results in a pardon or at least a commutation of his sentence.
Personally, I would like to see Snowden prosecuted for the crimes he's accused of and given a trial by his peers. I would very much like to see him get a fair trial, with all the evidence and arguments heard. The outcome of such a trial would be of great interest to me, as well as whatever happens afterwards. We would all learn something from it. It might suck for Snowden, but he thinks he's doing all of this to teach the American people about their government. The way his trial is conducted would certainly teach us all about our government.