The integration to the Terminal is awesome... people have mentioned "open /path/to/app" already, but:
"open ." to open the current dir as a finder window.
"cd " then drag a folder from the finder into the Terminal window, it puts the full path in for you.
drag n drop text from one Terminal window to another, or from the Terminal to the finder, or from the Terminal to Mail.app, or from just about any app to Terminal...
I won't be giving up on Linux entirely, it's still my preferred server platform, but OS X for all it's sluggishness is still the best OS for my needs.