At least 2 things: 1. treat N900 and Maemo a little bit more seriously. Device should have ALL functionality available in "closed" phones created with at least the same quality OR there be CLEAR info, when this functionality will be released (year, two ?). It would be excellent too, when they will have plans to make Maemo third main line too (but not in the most expensive devices only !).
2. give a real support for users of all their phones for people working for example with Linux. Library or something like this. Able to get/set calendar, pbk, notes and few other details. Or give help with this for Open Source projects.