I've been in situations where the GA has called for boarding all passengers at the same time (no first-class/elite preboarding), and there usually has been a reason for this such as relatively few passengers on the flight. Waiting for a recent flight, if I'd known the GA was going to call for general boarding literally three seconds after announcing first-class/elite preboarding, I would have worn my track shoes.

The gate area was full of passengers (mostly sitting) waiting to board the NW flight. I was sitting about 20 feet from the gate. The GA called for first-class and elite boarding. Being ready to go, I immediately stood up and started making my way to the gate. No one was blocking my way or crowding the gate area. I was about halfway to the gate when (exactly 2 to 3 seconds after her first announcement, and could have been in the same breath) the GA announced general boarding. The crowds closed in like the Red Sea.

While I was caught in the middle of this rush, being in the middle I didn't have to wait too long to board, or be overly concerned with finding overhead space for my carry-on. Neither was my flying experience itself adversely affected in any way. I was just a little surprised by the boarding experience. Why even announce first/elite pre-board if you're not going to give them the time to make it to the gate?