In fact the only way you find out is to ring your deskie direct
now we are promoted by e-mail
it rather depends on how many Xmas draws and Summer balls one organizes
I went to a USMC friend's promotion a couple of years back - they made such a big thing of it, formal parade, getting the rest of the troops out to support and congratulate him and his Colonel was delighted that I had made the effort to go along and pin his new bars on.
I know it's not quite the same thing, but when I got my Flt Lt, there had been a bit of discussion as I had additional qualifications which they were trying to work out whether they would give me early promotion. I found out not by email, talking to the desk etc, but from an SAC in PSF who was vey apologetic when I rang and was told "oh by the way Sir, you do know you're now a F/L don't you? It came through 2 days ago."
All really rather depressing isn't it and quite a sharp contrast with the situation highlighted above .... when people put the effort in and work their nuts off but the system can't be bothered to tell them in a decent manner that they have been promoted. Really does give an indication of how people are viewed by the system these days. And JPA and automation is no excuse - if the US forces can do it with their automated personnel systems, why can't we?