I think they both have a place - atom-notebook (like the web version) for more structured use with cells, and hydrogen for ad-hoc ("Will this work?") anonymous execution while you're editing.

Will I get no output except the output of the last line?

If the return value is one line, it prints neatly after the executed block. If it's more than one it inserts a little pane with the results, with options to copy the data or open it in a new buffer.