September 16 has been described as a day of immense brokenness at WordPress.com. There certainly seem to be more problems than usual. That several of them are related to categories adds some weight to the theory that code from WordPress 2.3 went in to Wordress.com over the weekend, and isn’t fitting as well as hoped.
I seem to have a magic amulet of immunity from brokenness, at least as far as WordPress.com is concerned. I’ve had no significant problems with the service. Even so, I’d like to see better communication, both before major upgrades to code, and after brokenness, especially brokenness of the largish kind.