Fountain of Knowledge

There's a difference between "talk like a kid" and "create a realistic kid's/teen's voice." You can get away with challenging words in narration, and you should -- kids who are reading absorb vocabulary that way much more readily than by vocab tests in middle school. But the conversations and internal dialogue have to ring true to the age group and time period.

For what it's worth, a lot of YA novels are not angsty, nor are they all told in first person. It's kind of insulting to YA writers to say that they all are -- I see this on blogs all the time, and every time I shake my head. Like with any genre, categorizing "all" the books as a single adjective is simply an indicator that the speaker has not read the genre very widely. Do a lot of angsty YA novels get published? Sure, because there's demand, and because of how popular shit novels like Twilight (and knockoffs) have become, there's more than a niche within YA for them. But check out lists like Teens' Top Ten, and there are plenty of gems.

Lorien