Does anyone have experience in translating the labels of the schema's in the content editor's GUI based on the language the editor uses in the CME 2011?
In a typical Tridion Blueprint, you have content created or translated in a single language per publication. With this in mind, Tridion allows you to localize the schema and change the Description of each field in the schema. So in your French translation publication, or your French website publcation you could have schema field descriptions translated to French.
Its not a full localization, so you cannot change the field definitions themselves, or add new fields, and if new fields are added to the parent schema, they will be added into the localized children. However this is exactly what you need to have local editors with field descriptions in an appropriate language.
Having schema descriptions change based on editor language is not something supported out of the box. If the above scenario does not satisfy your requirements, you would have to look at a GUI extension.