It may have been breaking but they did well to state that it would be breaking and was in development long enough (with RCs) that no-one should be caught by surprise.

I say this as someone who launched a site based on 2.3 as 3.0 entered RC status.

But doesn't "supported" mean iteration? If you don't want to use them why do you care if your framework is "supported" or not?

I launched an app the week before BS 3.0 launched and had to spend several days upgrading.