One thing I don't particularly like about the Drupal multilingual support is that it lacks a possibility to have separate settings for the UI, both backend and frontend, and the content. Personally I would prefer to be able to set a default language for the UI on a site, but be able to access content in other languages I understand as well.
In a perfect setup, I would be able to go to my account, set the language I want for the UI. Then also select all other languages I understand, including the preferred order that Drupal then will select from when content is available in more than one of those languages.
One problem with this, which also exists today, is that the language I view the content in, might not be up-to-date with the original content. I.e. that the original article have been updated, but the translated version I am reading is based on an older version. In these situations it would be great if it was possible to highlight this for the viewer so that they easily can switch to the updated one. If the updated is not among the languages I have configured, I should still be informed that I am viewing an older version.
Separate settings from backend (admin) and frontend would also be very useful. Then site admins wont have to make sure all languages the site supports are fully translated for what is exclusively used on the backend. Often it is actually more annoying when admin pages are translated as well. For large organisations this can also quickly become a quite costly operation to keep updated and supported.
Is this something that the multilingual improvements planned for Drupal 8 will address?

Comments
separate ui and content language
Separate UI and content language is already supported in Drupal 7, although the built in content translation module does not take advantage of that. The entiity_translation module exposes the functionality and lets you configure them separately.
A separate administration language option is a very often requested feature, see http://drupal.org/node/322995 where it is currently being tracked. (There is a module for that of course in the meantime: http://drupal.org/project/admin_language).
Great will have a look at
Great will have a look at that, thanks.
I assume that having user configurable language fallback settings isn't available now, but would it be possible to create something like I mention in the OP.
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/thomas
T: @tsvenson | S: tsvenson.com
various features
You mention various features in the OP, user configurable languages is a possibility and you can configure it as a fallback. Best to try :)