Just updating this a bit since things in Lucid are slightly changed, but the core issue is still there.
1) With Lucid, the indicator applet (as opposed to the notification area - my terminology wasn't precise in the original bug) does keep a static order, which is an improvement over Karmic.
2) The indicator applet an the notification area no longer have the one-pixel border issue seen in Karmic. If either is in right most corner of the panel, the icon is click-able by throwing the mouse in the corner without having to target.
3) However, due to the messaging indicator being the fixed right-most indicator, I am still unable to configure my system to have the volume indicator be in the corner. This continues to be a frustration, because manipulating the volume of whatever I'm doing is one of my most frequent actions throughout the day. Instead of being able to just throw the mouse in the corner and scroll, as was possible prior to 9.10, I have to carefully target the 24x24 px icon. It's quite distracting from whatever task is at hand.
I do get the sense that with the new desktop design initiative, Ubuntu is less interested in this sort of feedback regarding non-default configurations, or requests for excessive customisation. So I'm not really expecting much to change here, but hopefully they'll take in consideration some actual usage stories (such as this one) in their future design reviews.