Mashable's current design is based on Bootstrap. You wouldn't know it to look at it, though - we used bootstrap-sass, ripped out the pieces we didn't need, replaced others as the design called for it, while still getting the benefits of the scaffolding.

When you treat Bootstrap as a foundation rather than the entire presentational layer for an application, it's really quite good. Unfortunately, many people throw Bootstrap into an application and call it done, resulting in a very homogeneous look-and-feel across a tremendous number of websites.