I just sent a message to my test list and it took about 10 minutes for delivery... so it is working.
Back in March there was a problem with the announcement list and everything that had been sent between a Thursday and Sunday had been lost... users were notified that if they had sent anything out during that period, they would have to resend it. The bummer for me was that was the weekend I had sent out a very time-sensitive message.
If your message hasn't gone through by now, you should definitely give Support a note.
Ever since then, I always try to check to make sure things seem to be working before I send out an important announcement. I have a "Test" list with only a few names on it that I send out to first. Once I see everything is okay, I use the real list. The back-up plan is a BCC email to everyone on my announcement list.