Workflow steps should make their console (standard) output available to Groovy script. Standard error might also be handy. This would be especially useful for the sh and bat steps, which currently only expose the return value.
Currently, if one wants to retrieve information from say an external command-line utility, the output must be piped to a file and read back in using readFile. This is both inefficient and cumbersome, as well as hides the output of the command from the console unless specifically using a utility like tee.