I know, its pretty retarded..... how hard would it be to of just do it correct in the first place. I can live with the pricing range being ?=xxxxx but not the categories.... cause like you stated, messed up the breadcrumb and if the category has a description, well there is none. Plus if you have site map on, then there will be the SEO links as well so google will index both so you got to throw up a nofollow on the layered links.
Possibly you could mod the template file before breadcrumbs of some sort to read current category and set it in proper spot to at least make the bread crumbs, category name and description work properly.... you would think this is fundamental to the system. i guess not....
I’ve solved the categories problem by manuallu building category listings by using the object of current category and writing something like $_category->getParentCategory()->getChildCategories() and then spining the result through foreach loop and using the getUrl() and getName() methods. If you know the structure of your categories you can use these methods to fetch siblings, children categories, siblings of parent category.. but you have to have clearly defined category structure and sometimes that is not the case
Did you do that to the layered navigation? i mean, i know how to do it, but it seems like with the layered it is a bit more complex, especially if you’re in a category, it will have to hide the one your also already inside of and who knows what else, like filtering out the categories itself from initial listing.
Also it allows you to optimize the specific categories and product groups for specific search terms on a template, which will greatly improve the performance of your store in search engines (Google, Yahoo, Bing, etc).