First off nice little plugin, It works really snappy and I like the pinterest style a lot. However here are some things I found that could make the plugin even better.
Pinterest setting needs better controls for post count. I would like only one initial row of posts, but no mater the setting it stacks, 1 will stack 2 rows in 1 column. 4 stacks 3 on row 1 and then 1 post in row 2. It acts a little funky.
Images should be cropped and/or scaled and not squeezed for thumbnails. Pinterest is the only style that scales images nicely, the rest do a rather ugly squeeze. Crop and/or scale would be a much better way of handling thumbnails.
The Widget is a bit rough. First there should be an option or it should be built in to not display on the homepage at all. As of now it's a blank space. Again better thumbnail handling is needed. For instance Pinterest should be scaled to the widget width, The others should take post setting into count and then scale accordingly. As of now images are again squeezed and don't dived the width evenly leaving ugly blank space. Modern due to it's style is the only one that looks really clean in the widget except for the image squeeze.