Personally, I do sympathize with Holden. He is an introvert in a world of extroverts. He is a flawed person who is aware of his flaws. As much as his hyper-opinionated state of being might grate on some readers, I respond with pity instead of disdain. Holden's opinions are part of his weakness, I think, and reading his character this way it's hard not to feel sorry for him and to feel some hope for change in his future.
I too just reread this novel for the first time in 25 years, and now as a teacher and an educator, I find myself sympathizing with him for very different reasons than I did when I was a teen. Now, I wonder what psychological diagnosis he would fall under: ADHD? Asperger Syndrome? something else on the autism spectrum? bipolar disorder? etc... I am frustrated by him but feel sorry for him for whatever is going on in his mind.
It's funny how age changes the perception of some characters. When I was a teenager reading Catcher in the Rye for the first time (in the late 1960s), I sympathized with Holden a great deal. It was a turbulent time, and revolting against their parents was something with which every teen could identify. However, when I reread the novel again two years ago, Holden's attitudes sickened me. His hatred of virtually everything and everybody had no real foundation, and his excuse-making for every wrong turn showed an incredibly immature side that I didn't recognize four decades before. What seemed like an independent streak in Holden was simply an immature jerk badly in need of strong parental guidance and boundaries.
I find it hard to really sympathise with Holden, as most of what he holds responsible for his 'crumby' life is down to his own perception. He has opportunities that I wish many of my students had today. That said, I can certainly empathise with Holden as I see his cocktail of malaise, anger, frustration and desparation in many of the young people I work with. I admire Holden as a constructed character, although I know I would find him exasperating and irritating in my classroom!