I prefer it over Chrome because Firefox is a platform, not a product that treats me like a dumb user.
I use it on my Android too. It's a little sluggish and still uses too much memory, however it has a killer feature - it syncs everything with my desktop. It syncs my bookmarks and my saved login data for various websites I use. Saves me from a lot of manual typing and it is so addictive I can't give it up. Plus I'm seeing progress and they've promised a native interface that will be more efficient.
The desktop version is pretty stable these days too - I'm on the Beta channel (version 9) and I don't have problems. Even the versioning problems for the plugins I use have been sorted out.
I still recommend it to people, I would recommend it even to my hypothetical grandma.
If people from Mozilla are reading this - thanks for all your hard work.