I think most have a panel per device. I have a 4 rooms in my home controlled via iRule on an ipod touch. I have a home panel with a link to each room. From there each room has a home page panel with links to each device panel, DTV, Music, Dune, PS3, Wii, etc. Then each device has its own panel.
On my Kindle fire version I skip the room home panel, as along the left side of each device panel is a link to the other devices. So from the home panel, pressing living room button links to the DTV panel of my living room as that is the most common activity. From that panel I can link to the other devices available in the living room and go to their panels.
I've found this to be the most logical and easiest to navigate for both myself, my family and even guests.
I'm sure there are some other ways, but I try to limit the number of pages in a panel, when you start getting above 2 or 3 pages in a panel it can take longer to load I've found, especially with lots of graphic intensive backgrounds.
I have also found that if you have multiple panels to create that are the same, in my case 4 rooms with Directv boxes, that it is best to create 1 panel and assign no commands to the buttons, then copy that panel 3 times, then drag and drop the device specific commands in to each panel. Saves a lot of time as laying out the button graphics for me is the most time consuming part of the process. Trying to make 2 panels have the exact same layout, bouncing back and forth to each checking column, row, width and height for a button is annoying I hope the builder gets the ability to copy a panel without commands at some point but until then this is the best method I've found.
Hope that helps, good luck with your setup.