Thanks guys -- it's a nice boost to hear you say that I'm good at the test, because to tell you the truth I felt awful about my quant performance. (I still feel awful about it.) And really, my score is merely average considering that I'm applying to top five schools only.
I've got the native speaker's advantage for English, so it's not fair to compare your own performance to mine if you're a non-native speaker (as many people on this board are). But having taught English to non-native speakers I know one thing that students of English always fail to do: READ.
If you want to improve reading speed and comprehension, you're going to have to find a lot of good books and read them. I'd recommend authors with slightly more complex grammar and longer sentences. Hemingway is out. Read every novel you can find by Dickens and George Elliot. Read the New Yorker weekly from cover to cover and you'll be doing really well. There's simply no substitute for building your "ear" for proper English. (I'd recommend avoiding publications like Business Week, Time, and Newsweek. These are not going to help you develop a feel for rhythm and idiom. In fact, they're riddled with errors.)
Anyways, I know that's probably the opposite of what you wanted to hear. There's really no substitute for lots of reading.
But you did include one really neat hint in your own response:
I seemed to do well on piece that I am interested in.
When you're reading those passages, you have to convince yourself that this is the most interesting stuff in the entire world as you're reading it. The way I get myself excited about these passages is to think of them as mini-lessons on a topic that may come up at a cocktail party. If I can read and understand the passage closely, I tell myself, then I'll be able to participate in the conversation and learn even more. Maybe that wouldn't work for you, but you can construct your own "fantasy" to get excited about the passages.
Again, reading various material about topics that are probably outside your comfort zone will help tremendously. This is why I recommend that you read the New Yorker (or Atlantic Monthly). These magazines are well written and they'll challenge you on topics that you might have avoided under normal circumstances.
As for why I didn't app to b-school after taking the test... I didn't graduate from college until 1999. I wanted some work experience to get the most out of my b-school experience. I believe that people who go to b-school directly from undergrad are shortchanging their education.