Running tilecreator in scratchbox does not work (Qt programs loading .jpg files via QImage/QImageReader segfault in scratchbox). Therefore tiles cannot be created from srtm.jpg, which leads to a segfault on the device when activating maps using srtm data on the N900. As a workaround, the data files (which are architecture independent) can be copied from a different build.
Fonts in the control widgets are too big, fonts in the map too small.
A stripped down version of the control box would help. The tabs itself take more than half of its space.
The main menu is currently stripped down and provides only basic actions. Other useful actions need to be added or replacement actions be implemented (e.g. plugin selection).
Maemo devices have uncommon partition layouts and sizes. In particular, space on / is quite limited, /home has more and /home/user/MyDocs plenty. Cached data could be written to /home/user/MyDocs/marble. See also XDG Base Directory Specification, Bug 230714 and this patch. When using /home/user/MyDocs, it would be nice to find a way that prevents the Maemo built-in photo application stop indexing downloaded tiles. This should be doable by adding /home/user/MyDocs/marble to the NoWatchDirectory entry in /home/user/.config/tracker/tracker.cfg. Could be done while installing or in the startup script.