You'll need a pillow and a sack lunch.
Hey, I know it's early days yet, but ROTK is currently (along with The Godfather) the only film in history to score of 100/100 on MetaCritic, based on the reviews of Entertainment Weekly, Time, Newseek, Variety and Hollywood Reporter: all perfect 100's.
Also, on Rotten Tomatoes, ROTK has a 100% fresh rating and an average score of 9.6/10 after 11 reviews. Pretty amazing.
I haven't even seen the first two. I can see me going to see the third and complaining about the horrible character development "It's like they just assume you know these people".