Some other aspects of this:
Create a (red) circle and a (yellow) star; select both, and go to the Fill dialog. It shows the fill colour as orange; if you tweak the colour in this dialog, then both circle & star get set to orange.
Undo so that circle & star go back to red & yellow respectively. Group them. Now the Fill dialog shows the style of the group rather than its members, i.e. it shows Unset. If you click on the "Solid colour" button, then both star and circle get set to orange. (At the XML level, the group, circle and star each have a fill:#ff8500 declaration.) Change back to Unset; again, the group, circle & star all have their fill changed to Unset, resulting in black circle & star (assuming no parent element has a fill property).
First, let me say that I'm fine with leaving the above behaviour unchanged: the finer points in this area may well need changing once we implement style sheets anyway.
The main inconsistency for me in the above is that the Fill dialog shows the properties of the group element itself (as distinct from the average of the fill colour of its leaves), whereas changing anything in the Fill dialog with the group selected will apply the change to the leaves of the group (as well as the containing <g> element(s) themselves).
A fun variant: make the circle have unset fill. Once circle & star are grouped, use the XML editor to add to the group element a `style' attribute with value `fill:green'. The circle will become green, and the Fill dialog will show green as the group's colour. (The star remains yellow, as it has its own fill property rather than inheriting from the <g>).
Compared to the first example, this variant has more value in showing the fill of the <g> element itself as distinct from the average of the leaves. If one considers this variant in isolation, then one might go so far as to want changes in the Fill dialog to affect only the <g> element (and the circle insofar as its Unset fill results in inheriting from the <g>), without changing the fill of the star. (As has previously been noted, this can act as a poor man's substitute for named styles until we have a gui for named styles.)
Again, I suggest not replying to this immediately if at all, and I'll repeat that I'm happy for the behaviour to stay unchanged even for a release. Just things to think about in conjunction with how Unset will fit into our conceptual framework.
pjrm.