This is an excellent plugin so I gave 5 stars. However, I needed to do a lot of work to make it match my theme, and if am to use it in another site it will need just as much work to style it for the theme used there. So I suggest some enhancements for the upcoming versions:
1. I suggest to remove completely the specific styling that comes with the plugin's widget and leave it for the defaults of the theme. So, no forced background color, border-bottom, etc. This way the plugin will smoothly integrate with any theme without needing much CSS work which not every one can do. Also it is much better to use the default headings of widgets.
2. The only needed styling options (IMO) are the float direction of the thumbnail and the thumbnail dimensions.
3. Also it would be great if inserting the thumbnail becomes optional, in case other widgets of the theme have no thumbs.
4. If the the links have a "title" attribute that points to the post's title it would be nice too.
5. Finally, if the styling that comes with the plugin is to be included, it would be much better to make it optional from widget's options
Many thanks and regards,