Don't scare-off or exclude open-source users.
It should definetely be set apart from windows laptops, to avoid confusion, but it shouldn't be labeled as a 'developer' laptop. I have encountered tons of developers including open source developers that use Macbooks, which are marketed towards the complete opposite of developers.
It should be marketed to open-source users.(It might scare away some open-source users if it is marketed toward 'developers', but developers will still be aware of it) Basically putting a powerful and attractive machine in the hands of open source advocates. Open-source users would love to have an attractive and high quality machine specifically made for them. Market it has the Dark-Horse of laptops, by appealing to the dark-side of consumers or something. Give it a similar feeling that the name Alienware gives off. Maybe even give it its own line?
1080p matte display
backlit, high quality keyboard
3rd gen Intel core i5+
5hr+ battery life
Slim, and durable casing
----> Graphics: The support for Optimus is bad, but many Linux users and developers like to game (or they ARE game developers). I would still want an Nvida card(sorry Linus), with support to turn it off in the bios at the very least. Maybe the situation will improve later on. I'm not opposed to AMD, and the support might be better, but I don't know
The keyboard should have the Ubuntu logo or Tux screenprinted on the super key( windows key), no stickers. This would definetely help the overall appeal in my opion, because otherwise it feels like a half-hearted commitment towards Linux.
If you're marketing it towards developers, there really isn't a reason it needs to be loaded with dev tools. Developers already know how to get their environment set-up. I would say to keep it as close to a default install of Ubuntu as possible(I would enable two-finger scrolling in the touchpad preferences by default though(If it works?)).
Personally, I believe it should be able to compete with the Zenbook Prime UX21 or UX32VD with a dedicated graphics card. BTW, I do graphic arts, casual gaming, developing, and game developing.