LESS-Shopify is a default, largely unstyled, theme for Shopify. It's purpose is to allow rapid, responsive development for Shopify using LESS.
It's markup complete, supporting more or less the standard bits most sites should need.
Anyone who want's to hit the ground running with Shopify. The markup for most things you can/will need is there, cleanly written and easy to modify. What little CSS is in use exists soley to make the functionality of the theme easier to view & understand.
Not all by its self, that's up to you. SPR-LESS is built in to get you started with prespecified breakpoints, mixins and shortcuts.
It's most useful when used with LESS, however it's still a good markup framework for Shopify without, and to that end the NoLESS branch will get you going (once I add one, heh).