But anyways, when pages use this already, it OFTEN pisses me off, when I want to look at a PDF in browser, but the web app/page is forcing me to save it to disk and then re-open it in another app.
What we _really_ need, that we _don't_ have a way to do right now -- is signal the browser to _prompt_ the user as to whether it should be saved or displayed in-browser. The browser could ignore unless it was capable of displaying in-browser of course. That's something we do not have any way of doing in a reliable way now with HTTP headers, and I wish html5 would add that, instead of duplicating a lesser feature which is both possible now, and frequently annoying.