My 2nd cruise (1st was on Carnival Ecstasy). My 18 year old daughter and I drove down to Galveston from the Dallas area the morning of embarkation. No problem, plenty of time. Parked at EZ-Cruise Parking: as 2 ships were leaving on the same day, it took a little longer than usual to park, but nothing unreasonable. However, the Carnival ship had the MUCH better terminal and RCCL was off to the side. The old Galveston terminal is not laid out as well.
Check-in was fairly rapid. Secured a beverage waiver for my daughter upon check in. On entering the ship, it was kind of confusing and bottlenecked. The map you get upon entry is letter-sized and must be folded to fit in your pocket. Go to the purser's desk on 5 and get the better, pocket-sized map. Had I known, I would have gone straight there.
RCCL handled the luggage much differently than Carnival. The luggage gets unloaded by the stairs on each floor (a MASSIVE pile) and then the attendants move the luggage outside your doors. I didn't like that--traffic much worse.