I received my new RMBP today and am beginning to transfer what I want to transfer. In the past I have manually transfered mail, but Lion seems a bit difference. When looking for the "library" folder under my username, it does not appear to be there, so putting my mail preferences from snow leopard in the same spot just does not seem to be an option. Is this folder now hidden in Lion? Or what do I now need to transfer from snow leopard to lion to have all 3 emails with all received emails on the new computer?

Yup, it's hidden in Lion. In the Finder, hold the Option key and click on the Go menu, and you'll reveal the hidden 'Library' menu item.

It's a hidden folder in Lion, so to see the folder to copy Mail into it, simply do the following...

Open Terminal, type this command, and press Enter:
defaults write com.apple.Finder AppleShowAllFiles YES
(To hide hidden files simply replace YES with NO.)

You need to restart the Finder to take effect.

Yup, it's hidden in Lion. In the Finder, hold the Option key and click on the Go menu, and you'll reveal the hidden 'Library' menu item.

This works too, but, I keep hidden folders shown all the time.

thanks, I got it now. Going to be a bit of an adjustment to Lion, I purposely kept away from it, the first version of OS X that I did not upgrade to immediately.