It looks like Twitter Bootstrap 3 is just around the corner! I’ve been using Twitter Bootstrap 2 for an internal project and have used it for other quick prototypes as well (including the first Twitter Bootstrap). It’s an awesome framework for quickly putting a nice looking user interface together.
Version 3 promotes itself as mobile-first. Which I guess is getting more and more important these days.
At a first glimpse it looks like for Twitter Bootstrap 2 users the grid system has changed the most. The default style has changed a bit as well. No more gradients and box-shadows as well (but it seems they will come back). Though you can always add them back I liked the default style of version 2. A full list of changes can be found at Github.
A post with the best new features in Bootstrap 3.0 gives more in depth information on what changed. Good stuff!