First of all I want say thank you for great emacs mode, which I using for planning my life and job. Org-mode is the best!
I used 7.7 version with some patches from development version. For example, patch which adds ability to cleanup items in agenda view (org-columns-cleanup-item function).
I very like columns view, which I'm using for agenda views. So, I found that %ITEM is not cleaned for agenda views are generated by org-tags-view. After debuging and some investigation of org-tags-view code, I found that items in agenda view generated by org-tags-view have no text-property 'org-complex-heading-regexp. In this case org-columns-cleanup-item does not clean items.
Then I found that properties for item are coped in org-scan-tags function. But org-complex-heading-regexp property is not coped here. I suggest to add this property in this function. Please, could you check my correction? I have no big experience in lisp codding. So, maybe this change have some impact to other parts of org-mode. Here is little patch for version 7.7: