Normally when I press b, the block reservation shows in red. I downloaded today's nightly build, but when I select any other tool after pressing b, the block reservation doesn't show anymore. I'd consider it a bug because the block reservation helps me greatly understanding what I'm actually building. Is this a bug or is this done on purpose? If so, please lie and say it's a bug and change it back in the next nightly build ;D. Thanks for any feedback!
Since the new menu structure was introduce the block reservation system (and the clearance cursor) are a tool. Therfore selecting another tool disables it. It is done so on purpose.