This is a Firefox addon that uses part of the security model of Firefox OS to create sandboxed tabs. Each sandbox is a completely separated world: it doesn't share cookies, storage, and a lots of other stuff with the rest of Firefox, but just with other tabs from the same sandbox.
Yup. I have had two brother printers so far. The first was about 8 years old when the paper feed became unreliable, so I replaced it with a newer (color) model. Prints great, takes whatever cartridges fit, works fine with Linux, windows and osx. Haven't tried network printing from Android or iOS yet.
Disclaimer: I probably print about five pages a month, so it hardly sees extensive use. I also don't print photo quality stuff, mostly role playing maps and characters for gaming sessions. But under those constraints, it's been great.