This is more of a feature request than anything. In the next update to Ultimate Branding, I'd like to see a Custom CSS field on the design page for the Admin Bar module.
While one could put CSS styles to overide the admin bar into a child theme, I think it would be simpler and more useful to have it as an option in the plugin. It will also allow the styles to be durable through a theme change. More importantly, when one is in the branding screens and working with setting up the custom admin bar it would be a logical place to input custom CSS for this. Styles input in this manner should apply to both the front and back end.
If you were to consider adding this feature, a cherry on top of this sundae would be to offer an option to "Begin with unstyled skeleton" if it were possible. I just started working on this and using firebug spent a lot of time figuring out to how remove the defualt WP styles from the admin bar. There are background images in different areas, bars, borders and a bunch of little things that just end up getting display:none just to get me to a starting point where I can see the admin bar as a blank slate to begin with. If I could just click a button and strip it down to a white background with black text and separators between the items, I would be in heaven and I could just get to work.
With so many people out there who appreciate the usefulness of it, the current heavy styling of it kind of looks people in because it is time consuming to get rid of everything. From a sort of design theory point of view, the load of css up in the admin bar, really undoes that you-can-control-everything aspect of WordPress and if you guys came up with a way to for us to easily get handle on it, that would be grand! Besides, for multisite, that admin bar is a great way to spread the brand across the network - us multisite operators really need to get this thing under control.