We have sailed three new ships immediately after their debut (one an inaugural sailing) and we had a great time each and every cruise. The biggest inconvenience was on one ship where the service was a little lacking. It wasn't that the service was bad, just not quite up to the usual standards.
There have been a few ships that haven't had the best reviews during the first few sailings for different reasons. Mainly just adjusting to the new ship, new crew working together, etc.
A lot of people prefer to be on one of the first sailings of the new ships. It is a plus for being one of the first to see the new decor, stay in the stateroom, etc. I have been working with a group going on Glory on one of its first sailings and may even join them myself! I love sailing new ships.
If you do decide to go on Glory during July, just keep in mind that it is a new ship and there may be a few bugs. And have a wonderful cruise!