I'm having trouble getting Drupal to use the .po files that I've imported. This is the setup:
Drupal 7.2
Languages: English (default), Swedish. Language negotiation is based on user preferences.
Related modules that are enabled: Block translation, i18n, Menu translation, Multilingual content, String translation, Taxonomy translation, Translation sets.
This is the scenario:
If I extract a .po file from sites/all/modules/features (this is a big site with over 10 features) using POTX module, translate a few strings to swedish, and then import the file through admin/config/regional/translate/import, the strings that were imported are not being used in the UI for a logged in user who has Swedish as default language. The strings are a mix of field labels, titles, menu items and field help texts. I can search for the newly imported strings at admin/config/regional/translate/translate and everything looks fine there.
If I translate a string of the same type using the built-in UI instead of using a .po file, the translation works.

Comments
Update: Although I'm still
Update:
Although I'm still having some issues with getting translations to be recognized, I found one mistake I had made. The Field Translation module hadn't been activated. Using the latest i18n dev version it seems as if the labels are being shown in their respective language. Taxonomy terms are still halting though. Some terms work, and some don't. Haven't found a consistency here yet.
/Adam Gerthel - Projektledare, Odd Hill
user editable translations
Drupal core does not support translation for user editable text. As you figured out, you should use i18n and import to the correct textgroup. Taxonomy vocabularies have specific settings as to whether they'll allow translation and how.