Experimental Timelines feature; New Binary Data plugin; Lots more.
Hello preview does not start/ black screen
There are other comments in this thread about this. Looks like they intend to release a fix tomorrow. In the meantime stick with the previous beta, and don't save your project with the newest beta if you want to be able to open it in a prior version.
I hope the preservation of the project will not affect its performance in the future.