@Aapo - you probably might have already seen that, but I came across that pages while working on another project and thought I'll share them here anyway. Debian wiki has some pages about porting packages to armel - the fixes for common problems https://wiki.debian.org/ArmEabiFixes and packages that are known to have problems https://wiki.debian.org/ArmEabiProblems . There is also a general armel-related page ( https://wiki.debian.org/ArmEabiPort ) which has some interesting information. Have you seen and read these pages (there are links to some other interesting bugreports connected with apt-get, etc.)? Some parts of Maemo could be compiled in ignorance to these stuff and thus break when combined with newer Debian-base with or without some special fixes (but I think you already know that).
Just wanted to share these links