PalmOS mixes top and bottom menus too, but has the saving grace that for most applications the menus only do the lesser-user tasks, 95% of tasks allow everything to be done through the main screen. The older versions of PalmOS were probably better as they were leaner and simpler.

Maemo tries too hard to make everything work all at the same time - menus, buttons, side options etc.

Maemo is the best place to start, because it's actually working and has all the building blocks we need. Firstly, remove elements from the UI that duplicate stuff, add to applications only things which make them all consistent.

Most people get so used to their preferred UI they forget its quirks and flaws. Was it Steve Jobs who once said "don't ask what we can add to make it better, but what can we take away to make it easier"... I would add "without losing useful features".