As I said months ago when this discussion was up, I think that
battstat-applet icon is far more informative at one glace than
gnome-power-manager icon.
Last time I checked at least.
I think the problem is that the icon has this grey border, like a
glass border or something... In any case, a good idea would be to
abuse a little more the colors.
Also, right now the tray is already over abused and I would be against
having to put yet another thing there. In a classic panel setup this
doesn't sound evil but in more customized layouts the story can be
different.