It Didnt Worked for me..but mine problem is that for example Gaim doesnt have an icon in the upper right.... I can make a new panel, but It wont work... To see the runnign apps, you need a 'notification area.' Simply right click on an empty part of the panel you made, and click "Add to Panel..." and scroll down to select "Notification Area."
You can also get the clock back this way. And the gnome menus, etc.
BTW, once you add the notification area, the icons of your current programs, such as gaim, won't show up until you restart them. Just turn gaim off then back on and you'd be back to normal.
Also, I'd suggest doing any future upgrades in Synaptic (in the menu panel: Computer > System Configuration > Synaptic Package Manager). First, go to Settings > Repositories and uncheck everything except archive.ubuntu.com and security.ubuntu.com with "main restricted" sections.
DO turn off the universe and multiverse sections of archive.ubuntu.com, and any other URI that is there, or you may have an unstable upgrade, depending on your pinning. Everything but security is rarely, in fact I believe never, updated once there is the final release of that version, but of course hoary does get updated.