The only issue I can see with app.set('charset') is that it's kind of duplication of effort with app.set('view options', { charset: 'UTF-8' });

Here still happens not correctly. When I use res.json(data) or res.type('json') even res.header('Content-Type', 'application/json'), the output content (Chinese words) are all in wrong encoding which should be expected in UTF-8 by default.

When I set res.header('Content-Type', 'application/json; charset=utf-8'), then everything goes well.

So I think this is still a problem.

BTW, I am using 3.0.6 now.

@mytharcher do you mind testing the latest express 4.x rc?