Binary package hint: network-manager
In network-manager-gnome_0.8.2+git.20101123t161608.f143e76-0ubuntu1, there are no icons for signal strength in the list of available wifi connections. The connections themselves are listed, and can be connected or disconnected as before, but there are no indications of the strength of the signal-a real nuisance for selecting open access points when names are cryptic and many are available in an urban environment.
The panel icon displays OK in gnome-shell and also in unity-compiz, and will show the strength of the signal that has been connected to, or icons for disconnection or a wired connection. It won't always show up until the network has been scanned, though, and disappears if you switch from gnome-shell to unity-compiz and then back to gnome-shell.