He is definitely guilty. He did the things with which they're accusing him. The punishment of that crime is straightforward.
However, I think he is a patriot and should be lauded for his efforts. When he did it, he knew that this was what he risked. He obviously felt that it was worth it to provide such a tremendous service to his country. I applaud him and consider him a national hero for making such a sacrifice for me and everyone else. I would like to think I would do the same, but without being placed in that situation, I obviously can't say for sure. He can. His moral character was tested and he passed with flying colors.
This is the way things should/need to work. If there weren't consequences, we'd have all sorts of deluded people releasing classified documents (that they - possibly errantly - felt needed to be released) because they thought they'd just be allowed to go on their way (the world needs to know that we use slightly too weak of bolts on our drones, so here are the plans to prove it!).
The best possible timeline for this type of situation in my opinion:
1. He releases documents and is exposed as doing so
2. He is arrested and tried for the crime
3. He is found guilty and sentenced
4. If the public good that came from the action is so dramatic as to warrant it, he should receive a pardon (but that doesn't mean he shouldn't have been found guilty to begin with).
Of course, I won't hold my breath for the pardon, though. Politicians are too concerned with appearances to risk being "soft" on "terrorism" (everything bad is "terrorism", don't you know).
I salute you Bradley Manning. Serve your sentence with pride.