Just a quick idea on the 'Customizable main screen', I love the look of the Front Row style layout but think that maybe a dynamic grid layout would be more practical.
This way we can have a preferences section where the user can decide which modules/sections they use and only they will show up on the main screen. As you say who uses photos, you can simply disable the photos button showing but still allows for people who do use the photos module to enable it.
I think some nice navigation effects would be pretty cool but could probably hold off on these until Leopard is finally released and we can use the CoreAnimation framework.
My comments here are on the 1.4version as this is the only code I have available.
What source are you trying to upload? I can try if you want, I used to use CVS but it has been a while now.