Firefox isn't exactly suffering in the looks department. The UI is simple and minimalistic but practical. It may not always be pretty, but it works. Mozilla is working on a major revamp though, it's been doing it for months.
On the desktop, it's a refresh of the current design, it's certainly better looking, but nothing revolutionary. Things get more complicated when you add mobile phones and tablets in the mix.
Mozilla doesn't just want a clean, useful and good looking design on the desktop or on mobile devices, it wants a unified
look and feel across all platforms, it wants Firefox to be Firefox no matter where it runs.
A simple way of getting Firefox to feel the same on all devices is common design elements. The UI layout and elements will be different, based on the specific requirements of each platform, but Mozilla plans a common design language across all.
Soft curves are something you'll see across devices, the mobile UI already follows this. Another common element will be the main menu, which will be accessible via a button, placed on a similar location on tablets and the desktop.
The new design is codenamed Australis on the desktop. There's an overview of what Australis looks like here
. On mobile devices, the redesign is already live in the Aurora channel, soon to be Beta.
The table and phone UI will share the most, obviously, tabs have been completely redesigned compared to the desktop version, the AwesomeBar suggestions look a lot better and, importantly, will look the same across devices.
Design is not the only thing unifying the Firefox experience, Sync plays a huge part in this as well since it will enable users to have their history, their bookmarks, even their last visited tabs available on any device they use.