Thanks for the great plugin. I added some small features that you can incorporate into your plugin if you feel like it, or not :)
The features I added:
* new checkbox in post/page metabox called "Force Show Before Content". I used this so I can by default not have the buttons appear (all settings unchecked) and then selectively choose which pages/posts to show them on. This is almost the opposite effect to the "Hide simple social buttons"
* new admin setting to capture twitter username. This adds a "via @username" to the the tweet when the tweet button is clicked.
* if the post or page contains a custom field named "hashtags", it appends that onto the tweet when the tweet button is clicked.