Yeah I am going to have one.
After meeting with our celebrant last night, she thinks that because our chapel is rather big, it would be worthwhile. She also thinks it is good to work out the timing of walking down the aisle to the music and a run through of where we should stand and when to hold hands etc. She did say that she thinks having the groomsmen at the rehearsal was a bit useless because they're already just standing there. But to include bridesmaids and the person in charge of your music.
I think it would be a personal choice. If you are going to feel too worried on the day because you're not 100% sure, then I would say have one. If you don't want to stress about organising everyone to get there and it won't make a difference - then you could probably leave it!