It should be obvious that he planned to take the data. Taking it without a plan would be a good way for him to fail to accomplish anything. The main detraction I can see is that he leaked without regard to content, even considering he may not have had time to look over what he had taken (e.g. there is some top level stuff about drones that probably could have been redacted with a quick scan of the documents).
He likely avoided commenting on improvements to remain apolitical; if he had not, it would be more ammunition for character assassination. Other countries may be doing roughly the same but most people's issue is not with the fact spying was occurring but that it was largely turned inward.[1] You do not know he would throw away the whole system. As previously mentioned, he likely had no time to figure out what documents were what and the impact of their release would be.
In any case, he was acting as if he expected his own government to completely ignore the protections it had built in to defend its citizens. That some of the domestic programs he exposed were since cancelled due to public outrage is telling.
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[1]: Besides the unconstitutionality of inwards-facing spying it is also a red herring. We repeatedly see little in the way of domestic terrorism but because inward spying is so much easier to do it seems to make up a disproportionate amount of the information generated; information that is likely not representative of real threats.