By the way, since there are a lot of first time HAL cruisers in this thread, I thought I might share my own opinion here. I see most people being very positive about the Club Orange upgrade, especially on the Pinnacle Class ships since they have their own CO dining room.
We tried to upgrade to CO quite shortly before our departure but it of course was sold out already. Personally, in the end we're glad we weren't able to upgrade at all. We luckily got upgraded from our VH cabin to a V cabin without obstructed view, which was great and also the best we would've got by paying for CO too (this of course isn't true when you book very early, when booking VH with CO seems a very good strategy to get the best verandah cabin). We didn't like the atmosphere and look of the separate CO dining room as far as we could see from the outside. I'm sure the service would be quicker than in the MDR, but overall we loved the atmosphere in the MDR and the service was very good as well. Sometimes not that quick, but always friendly and personal although we did the open seating. Only had to wait one time in two weeks and that was only 5 minutes.
I think CO is a great option when you book very long in advance and are able to pay for a VH cabin and get upgraded to a much better cabin, but in other cases, I would really think about the fact of having a separate dining room and maybe a slight upgrade are worth the cost for you. For us, it wasn't and we we're glad we didn't had CO.