This is a very nice plugin. Actually I've been using a similar plugin called Select Shortcode Exec PHP and it has an option to allow executing shortcode in Widget text area. It is very useful so I'm wondering if your plugin can support that functionality. I find your plugin admin panel is very clean and simple. Also both HTML and PHP support is very nice as well, while the other one only supports PHP code. If the feature is supported, I'd like to switch to this plugin.
Anyhow, this is my feedback and have a nice day.