Convergence is key
The Ubuntu phone is an interesting idea - many are predicting it to be dead on arrival, since Canonical is so late to the game with their mobile OS here. Whilst that may be true, and Ubuntu for Phones might not see much traction, there's a bigger story here that is more important.
The Ubuntu phone marks a significant milestone that nobody else in the mobile business has managed to nail yet. It runs the same codebase as the rest of the Ubuntu family, meaning it can be docked and used as a real computer or synchronized with a slab and turned into a tablet. Microsoft has long heralded the shared codebase of Windows 8 and Windows Phone 8 as one of the biggest things the company has done, but whilst they're shared, they aren't one in the same and you can't just port an application across (nor can you turn your WP8 device into a real computer).
Bringing the computer and the phone together makes for some wonderful use cases. For example, you get to work, dock your phone, start working. Suddenly, you receive a text message. It just pops up as a notification on screen and you reply and carry on. No need for pulling out another device to interact with. This could apply to phone calls and interacting with mobile applications on the desktop too.
Even if Canonical fails with Ubuntu for Phones, it's a huge leap forwards. This is the first piece in the puzzle of showing people that you only need one device to power them all. It's the first step towards using your phone as your desktop computer. Over the next year, I'd say we'll see a slew of other platforms and OEM's do something very similar to this.
This is a huge space, so make sure you watch it closely.