I haven't gotten my baby yet. He's only 1 month old.
You can check out the Growth Chart Sticky at the top of the General Discussion page, and it will give you a general idea about how big your baby will be. Its not always accurate, but its fun to look.
There's also a lot of people on here that got big puppies, but they stayed small dogs...and lots of people who got teeny puppies, but they got a growth spurt and became teapots!