I came across your plugin after searching for a way to bypass my theme's hard-coded image attachment function (which only registers featured images when uploaded through the post/page editor). This morning I installed to test it out and ran into a few problems...
1) The drag and drop box did not look anything like the screenshot on your plugin page. It looked similar to the native "select featured image" box with two buttons for selecting or uploading a featured image.
2) When I tried to drop an image from my computer into the box (while in the post editor), my browser reloaded and just displayed the image (as if I had pasted the image URL directly into my browser bar). When navigating back to the post, the featured image box was empty and no image was set after publishing.
3) In testing the select image feature, I was able to choose a test image that I had already uploaded to my media library and after publishing the thumbnail successfully populated on my test category page, but the actual image did not pass into the post's designated container for the featured image.
4) I also tried uploading a new image by clicking the "upload" button within the box but the image I selected fom my computer did not attach or display within the post editor's featured image box. Strangely, when I checked my media library, the file name of the image was listed, but it was shown as an unknown mime type. For some reason WP did not register it as a PNG.
I've debugged in IE9 and FF to check for script conflicts, thinking it might have to do with incompatible jquery, but suprisingly no errors were generated. The only thing I can attribute this to a built-in function in my that builds galleries through images uploaded in the editor for a specific post.
Here's a snippit from my function.php that enables this feature: http://pastebin.com/3M8uKYxR
And here's the hook in my single.php to execute the attachment feature:
Although this is something that probably falls outside of the scope of providing support for your plugin, I'm really hoping you can shed some light on how to disable or work around this built-in roadblock as it really eats away at my time (typically I publish 75-100+ posts per day). I was excited when I came across your plugin last night, and really want to make it work so I can streamline the steps involved in publishing these posts.
For refernce, here's a link to the theme I'm using: http://tinyurl.com/ck8cndb
I wish I could provide the URL to my actual site, but am unable to share it publically because it's used as a private portal for client access only. If you want to take a look, just let me know how to reach you outside of the forum and I'd be happy to send you the link and login credenials.
Thanks in advance for any assistance you can provide!