We are using the HeadTag plugin for a while now and it great! We have moved the head code from our templates to this plugin so this keeps our templates 'cleaner'. Also the plugin gives us some handy extra features.
I do have a minor issue with the layout of the plugin. Especially the filed 'Script or Styleheet URL'. The URL's we use here are always longer then the available space and we have to scroll inside the text field to see the whole URL. It would be nice if this text field had some more space... Maybe even a text-area like the custom tag field?
I think maybe the header cell has a bit to much text to be able to make other columns smaller? Maybe the headers info could be in a separate space on the page, or as a popup above an i button (info) or something? This might make it easier to control the width of the columns?
Also the 'title' of the page (like 'Access levels') could be above the table?
Just some thought to make it easier to navigate around the tag settings...
I can't do anything about the "Access Levels" label, as that's a core Joomla construct - a function of the /administrator template. The individual column descriptions though, I could definitely move those somewhere else.
Switching the url field from a text field to a textarea is also an easy change.