Depends on the airline and the airport too. I have never once had it weighed though - it is counted as an item sometimes, but never weighed!

Sometimes you can take it all the way to the plane door, sometimes you can take it to the very last waiting lounge, and sometimes they take it at check in (Cairns!).

I contacted air NZ once and they said I'd have to check it in with the luggage, but they actually let me take it to the gate. Then next time I had to check it!