Well I'm pretty stoked to hear that...http://svn.silverstripe.com/open/modules/sapphire/branches/nestedurls IS the place to get the latest version?
I've basically had problems I've had so far:
TreeDropdownField - needed to remove a section of TreeDropdownField::tree() that was throwing the "TreeDropdownField->tree(): the object #$ID of type $this->sourceClass could not be found" exception...just commenting out that block seems to make it work fine.
Folder - had to remove the code that adds the "Unused files" tab because it didn't think Folder_UnusedAssetsField existed, or something to that effect.
Form - had to change "return $this->controller->Link($this->name);" to "return Controller::join_links($this->controller->Link(), $this->name);" in Form::FormAction() so the tree dropdown in Image fields would load. Otherwise it had a "Action 'field' isn't allowed on class Image_Uploader" JS error.
Also commented out the "if($this->validator->getErrors()) {}" block in Form::FormAttributes() because little popup forms in the CMS had [null] validators and it was causing an error.
Of course for all I know I might have managed to download and old version or something...