This plugin removes the mandatory 'Category Base' from your category permalinks. It is compatible with WPML.
Use this plugin if you want to get rid of WordPress' "Category base" completely. The normal behaviour of WordPress is to add '/category' to your category permalinks if you leave "Category base" blank in the Permalink settings. So your category links look like
myblog.com/category/my-category/. With this plugin your category links will look like
myblog.com/my-category/sub-category/ in case of sub categories).
As far as I can tell, no. I have been using this on several blogs for a while and it doesn't break anything.
Simply don't have a page and category with the same slug. Even if they do have the same slug it won't break anything, just the category will get priority (Say if a category and page are both 'xyz' then
myblog.com/xyz/ will give you the category). This can have an useful side-effect. Suppose you have a category 'news', you can add a page 'news' which will show up in the page navigation but will show the 'news' category.
Depends, if its useful enough and I have time for it.