The above pics are a good dose of reality, but a few more words might help.
As above, the terminal doesn't open till 11. So, if the poster who suggested showing up at 10 does that, he/she won't even be allowed into the area until 10:45--detour to McDonald's or arrive later!
If you show up before your scheduled arrival time, it is up to the CM whether you will be allowed into the terminal or have to wait a while--this is to keep the occupancy within the fire regulations. However, getting in early won't help you because your boarding time is tied to your scheduled port arrival time (not your actual time.)
The times DO go more quickly than they are scheduled. Boarding starts at 11:45. If you arrive at 12:30 on the classic ships or 1:00 on the new ships, you will walk right in, register, and walk on. By then the crowds are have boarded and the terminal is relatively quiet! The WDW bus traffic will arrive at 1:30-2, so there will be a brief rush at this point.
Finally, if you are on
DCL transportation from MCO or WDW, you will not have to wait to enter the terminal. I've been held on a bus for about 10 minutes (presumably to let the crowd thin a bit), but once off the bus you will walk into the terminal. If coming from MCO, you will have already checked in and be ready to board as soon as your number is called (and you got the number at MCO).
AND finally, lunch is served until 3:30 (when everything closes for the safety drill). The venue you would have preferred may not be open, but you won't go hungry.