Anyone who has used Bootstrap's mixins with semantics in mind knows there are some bigger issues to address than the layout. Some questions off the top of my head:
* How do you build semantic forms with Bootstrap without going to markup fluff hell?
* How can you avoid the unsemantic class names for components that are tied too closely with child components (I'm looking at you, .panel)?
* What is the semantic purpose of a row element? It seems purely presentational to me.
* How do I add icons without peppering span.glyphicon.glyphicon-X's all over my markup?
* How should I organize/maintain all of my LESS files as my stylesheets scale? I'm not looking for any one "right" way, but suggestions are always nice.
* Are there any optimizations I can consider when I'm only using a bit of Bootstrap's functionality?
* How can I extend Bootstrap's mixins for my own needs?