Went to dinner on a Saturday with no reservation. I had to wait 2.5 hours for a table of 5 and to be honest I was really upset when I sat down. I was told it would be an at most 2 hour wait.
Here's where everything changed. Imagine a restaurant where you have a great steak and by the time you finish off your last bite, a man with a sword of meat drops more meat on your table. This continues for about an hour until you literally have to say "No thanks, I can't take this anymore"
In any normal establishment you would stop yourself way before an hour of constant eating. It's extremely difficult to stop at Copacabana because it's actually that dam good.
On Saturday they have 13 different meat floating around the restaurant and you should try all of them. There were some things like the suckling pig that were not brought out unless requested. Look at the menu, make sure you try everything and if you don't see something just ask for it.
Overall great experience and I forgot all about the long wait by the time I ate my first bite. If you want to go on a Saturday, make a reservation and know that in order to get one after 4:30pm you have to make the reservation 2 weeks in advance.