This may or may not be related to what you want to do, but I've done this on a couple of sites now:
I don't what to use a treeview menu and instead want customers to drill down through thumbnailed categories until they find the products they want. To achieve this, I use the submenu feature that is in the product list module settings.
The problem with that is that it continues to display the category thumbnails when one is viewing the final category full of products. To get around that, I insert an style tag into the productlist template that hides the category menu at that point - Something
like this:
#dnn_ctr4077_ProductList_pnlProductList .CategoryMenuWrapper{display:none}
So that the buyer can browse back up the categories again, I add a category menu above the list and set it to display only breadcrumbs and hide when root.
You also need to ensure that categories only contain products or sub-categories, but not both, and you also need to disable cascading in the productlist module settings and also have a default category applied - also in the list module settings. Make the default category "All Products" and ensure that all other categories are inside it.
That's all a little goofy but it results in a store with proper category drilldown and allows one to dispense with a treeview.
Regards
Rob