Handful-

Excellent work. This continues to be a leading UI framework for the Maemo platform.

In watching the video, I had some thought about the menu UI. Using the grids is a great enhancement to the previous methods of interface. However, once you are in a sub-menu (2nd level), the UI goes back to "arrow" interface mode again--the icons on the left and right of the screen go to the next and previous sub-menu (2nd level). This is certainly better than simple arrows, since it give the user information about which menu will display next.
But...I wonder if you can make it even better. Instead of two icons (left and right), can you make a smaller grid or maybe a column of the icons from the top-level menu? I can imagine a few ways this could work:
1) "Parting the Red sea" method: The top-level menu icons get shrunk and split to two columns on the left and right of the screen, with the sub-menu displayed at full size in the middle.
2) One-side/"dock" method: The top-level menu icons get shrunk and positioned on one side (or along the bottom, like a dock)
This technique would allow the user to get directly to the menu they wish, rather than (potentially) having to click the left/right icons multiple times.

Another idea would be to have a "home" type button on all menu screens, which would jump the user back to the top-level menu, instead of having to press "Back" multiple times. (Yes, this idea is similar to the iPhone "home" button, but it would a UI-button rather than a hardware button)

I must admit that I do not yet own a N800/N810 (though my birthday is coming, so I think that will change! ), so I do not know if these ideas are practical given the small constraints. Obviously, the more icons in a given menu, the smaller the shrunken versions would have to be in the lower-level menu. But it seemed like most menus would have a maximum of 6 icons in the grid, judging from your prototypes.