I'll mention another of ysss' accursed word (android/g1) ... but this works just fine in Android. They cheat a little, which you can figure out from using it a little bit ... but it does have a grid of home screen objects. The grid is basically a 4x4 grid, and objects can take up 1 or more grid spaces (have to rectangular, but it could be a 4x1 grid, a 3x3 grid, etc ... application icons, by default, are 1x1 though).

You can rotate it, and the grid just rotates. And the image behind it. You do get different views of the background image when that happens (the closest way to describe it on a NIT would be: the background image is 800x800, and you see different sub-sections of that based on whether you're in portrait or landscape ... or, if you don't like that android-ish method you could simply re-scale/re-stretch the image on each rotation).

Part of their cheat is that: it's a 4x4 grid, in the middle of the screen. 4x4 rotates quite easily. The other cheat is that the bottom of the screen (in portrait)/right side of the screen (in landscape) is taken up by the application tray, which helps hide the fact that the grid is only 4x4, and not the whole screen.

In Maemo, you'd probably say that the grid is (in pixels) 480x480, centered on the screen. The area to either side of the grid could be for special things, or just for "see through to the background image" area. They could even be for certain universal buttons (answer call/dialer, browser, calendar, reject call/screen saver), and the other area could be for status symbols (an envelope if you have email, something else if you have SMS messages, something else if you have a missed call, something else if you have a voice-mail, etc.; click on the status icon to pull up that application).

Within the 480x480 area, you'd divide that up into however many grid spaces you want, as long as each space is square, and evenly divides the 480x480 area (so, for a 4x4 grid, each space would be 120x120). And then you can allow widgets to take up a 2x2, 3x2, 2x3, 3x3, 4x1, 1x4, or maybe even a 4x4 area (assuming you did a 4x4 grid).

And, note that those last two paragraphs are JUST for the home screen, not for the user interface in general.

I don't know about anyone else, but that'd be good enough for me, for the home screen. I could use it for quick status checks and to launch other applications, and not have to care what orientation it's in -- in any orientation, it will still work. No worries about how I'm holding it, no worries about reading the text or recognizing icons that are rotated away from horizontal, etc.