As you might expect, there will not be many differences between Chromebooks in terms of software, since they will all run ChromeOS. I think that each vendor could probably choose a different color of the icons and install different web apps according to their preferences. I'm not expecting much more than that in terms of visual and software tweaks.
For instance, it wouldn't be unexpected that Samsung could install some sort of Android web app to manage their Android devices, like Galaxy S & S II. It's just an example and something that I would love to have on my future Chromebook.
Here are some screenshots of ChromeOS on the Samsung Series 5