I have a 3 year old right now :) First of all, she cracks us up with the stuff she says. They start to pick up little phrases, idioms, etc and try to use them. My daughter often says "seriously!" and "it's for reals" when she wants to emphasize something and it's the cutest thing.
She still wants to express her displeasure with squeals and shouts and crying instead of words though- we are working on that. I remember that being a big thing to work through with my older daughter too. They seem to be really blowing up in the verbal communication department, yet they still resort to emotional cries and noises when they are mad/sad/upset, rather than "using their words" (<---a parental phrase that I can't stand btw! its so cheesy!)
It's really cute to observe my daughter playing in her own world- talking to her dolls, toys or stuffed animals and creating her own little stories.
She gets in a lot of tiffs with her sister, and the two of them get into shenanigans when we are out and about together, but one-on-one she is dream! I could spend the whole day with just her and me and she'd probably last through all kinds of errands (as long as the snacks were flowing ;) A 3 year old is nice and portable and good company.
Enjoy!