Category Picker: big performance issue with new picker and underlying script

I uploaded the category file from the geneva counties (QA import file for categories).

With root, I am trying to expand my tree and select some categories (with FF2). Quite rapidly I am getting some script error (Le script ne répond pas) and this is taking minutes in order to select a category.

Clearly speaking I am NOT in favour of selecting automatically all parent nodes of the category tree. This is clearly not a best practice. If we want to implement something like this, this should be done at an API level in order to offer alternatives to look for all children or all parent objects. But this should not register dozens of category automatically.

Moreover, you can now subscribe to one single object in your tree by using the "List" search tab but not using the tree tab. this is not consistant.