A feature I loved a so much on OS X is the Safari smart zoom (like double tap an area in Safari on an iphone/ipad). I do not like reading blog articles or any kind of texts with a small font size. Instead I prefer to read in full screen (27’ iMac).
I would love that this feature is supported by the graphical server (X11) (maybe Wayland would support it ?) so that it could be used outside of the web browser like when opening an image or a PDF.
Iceweasel is a Debian version of Firefox which mainly change the name and the logo (with some Debian patches) which means that the Firefox add-on work.
There is one which do exactly what I want and it’s Zoomr. Install it and then hold the click on the area where to zoom. : )