I wouldn't be so quick to assume it's working for everyone.

Some people had issues on my server downloading certain files because their browser interpreted them incorrectly. I had to add a MIME type declaration in the base .htaccess file to ensure it works for everyone. The last was with dmg files.

I've also seen plenty of sites where PDF files will not open inline, but I've never bothered to check why. I'm sure their web masters weren't going to send me a check for my time and i had other stuff to move on to.