Having just done a Miracle to Alaska a few weeks ago, I can tell you that the boarding process is HORRID in San Fran. I do not think it's Carnival's fault, but the porters there were slow and disorganized. When you arrive, the porters do not take your luggage, but instead make you get in a series of long lines, and they grab your luggage when they get to your line. Seems easy enough, but they made a mess of it.
My older parents had an 11:00 check in. My wife and I had a 1 PM check-in. When my wife and I got to the port around 12:30 ish, my parents were still in line. There were four long lines at that point, that were indiscernible at first glance. However, I did venture to the front and noticed 4 small signs (11, 11:30, 12, and 12:30. Being that there was no 1 PM line yet, we went to the end of the 12:30 line to wait.
Fortunately, it's San Francisco, so we were not waiting in the 95 degree Florida sun, but it was 2:30 before we had our bags taken, and got to go into the terminal to check in. Once we were in Carnival's hands, the checkin line took maybe 15 to 20 mins, and we were on the boat by 2:45-3:00. Yeah, the boat was late to leave....
Even funnier was the the return. Since were in the back corner of the boat, we got to hear the dock workers' expletive laden argument with the crew about how to secure the tie ropes to the dock. Then disembarking at 9AM, there were already passengers lined up to get on, and I got to hear one woman lay into a porter about why they wouldn't let her board yet (besides the mess, she was an hour early, and passengers were still getting off from the previous cruise. I love people....)
One other minor annoyance - SF has these little fly-gnat like things that are EVERWHERE, especially at the Alcatraz tour docks next door. They don't bite, but they do swarm and annoy the crap out of you. Some of them stowed away and rode with us to Alaska (contained to the balcony). There weren't enough to be annoying anymore, but we were two stops/5days in before I stopped seeing them....