Make it work with a vanilla image
First of all, thanks for doing this - good Linux-support is very high on my list of required features, and has been a reason for buying Dell in the past.
You write "The image will come with the necessary drivers to support the HW" and I have to ask: isn't it possible instead to update the machine's firmware, so that it is sufficiently standards-compliant to work with a vanilla Ubuntu image?
If the machine requires a custom image, that leads me to worry that it will need customisation for every new version of the distro in the future, and that reinstalls might be a hassle every time. It also suggests that it might prove a hassle to install other distros, which lack your customisations.
Dell appears to have a fairly good track record of building laptops that "just work" with Ubuntu: at least quite a few are listed at http://www.ubuntu.com/certification/desktop/ - so please make this another one!