I just tested this plugin (great concept and much needed, thank you!) by sharing a link. I picked a thumbnail, wrote in some of my own text and submitted. The formatting is less than ideal. I tried a few other post formats and they all had (what I perceive to be) the same problem.
It seems like what I write would be top priority, then a thumbnail (or image, video, whatever), then the link to the original source. As it stands now, it's the link, then (at least in my experiment) a mess of "thumbnail" and my note.
In my example, it didn't actually generate a thumbnail, it pulled in the whole image. I can work around this, but in an ideal world this plugin would actually pull in and resize the image we pick.
So if I were to do a list of things I would love in this plugin:
1. Put my note on top of whatever I'm sharing and the link at the bottom (thumbnail in the middle)
2. Grab and process the thumbnail locally
Otherwise, very cool and exciting!