Updated to 2.9 today, and went to publish a post. Can save drafts, but when I hit publish, the post "refreshes" as it normally does when doing spellcheck and then freezes.
I deactivated Jetpack, went to the draft post, and all text was missing. Previous revisions were all available. I was able to restore from a previous revision and publish the post (without Jetpack) with no further issues.