I'm not sure what the best approach is here, though, so any suggestions are welcome.  My hope was to have a right-side label and not break the block-level layout of rs-progress.

The set-variable-width-progress mixin sets the width of the borders and .rs-progress-inner so that the .rs-label can float left agains the right edge of rs-progress-inner, keeping the overall progress bar a block level element.

I guess this could present problems if the label width + progress bar width is greater than the max-width originally set for .rs-progress...