First, let me say that this is a brilliant tool... it seems to work but I have one minor problem.
I'm using the Custom Post Widget plugin to enable me to create content blocks that I can then use with WP Page Widget to show on a specific page. I'm doing this because I may have a piece of html that I want to show in a widget area on say 5 posts, and a different one on a different set of posts and so on. This is so I can show links to a specific product on different post pages. So far so good. It works a treat.
The problem is that when I go to edit the customised plugin, it just isn't visible in the Sidebar area under the Page Widgets meta box on the post edit page... it isn't an issue with functionality as the changes still seem to work but it does make for extra work in editing and updating.