Last year was my first year at NAF, but I'll tell you what I can about it.
NAF is a fairly small con, so don't expect areas to be packed. That being said, it's fun (in my opinion at least). Usually there's a few things going on at a time... last year there was one room for panels (I'll be running this year hopefully... I need to get my sheets in though!), one room for gaming, one viewing room, and a dealer's room/artist's alley. There's a masquerade, where people can put on short skits and show off their costumes, and a JPOP dance. There are other live shows throughout the weekend, from anime improv to hosting to musical performances.
And don't worry, you'll see a fair amount of cosplayers wandering the hallways. ^_~