I would have to say that I mostly feel empathy. A lot of the things he talks about that really bother him are like perfect articulations of what I think about sometimes. I love it when that happens. When you think "yes, thank you! someone understands!"
I also obviously have judgement. It's hard not to make judgments, and they are often subconscious. At the beginning, I expected that he was not a kind boy. I had that presumption because for one thing, he is failing his classes, and he is also kind of sarcastic in his manner of speaking. It's easy to forget that just because someone doesn't care about some things, doesn't mean that they don't care about other things. He is actually a lot nicer than a lot of teenagers, because he is thoughtful about things. He notices when something is happening when it is not obvious, like when he is so concerned with the professor feeling the fault of Holden's failure. Holden noticed that was happening. Many teenagers only think about the obvious things because they don't care enough to try to discover other things. They go through life just caring about their own thoughts and feelings, because that is what affects them.