I often do something similar (only using the Pause command instead of @leavedoswindowopen), but it's also worth mentioning that extra processing can happen with DOS Batch buttons which doesn't happen for normal buttons.
e.g. Percent characters are doubled-up in filenames to avoid DOS treating them as something else.
It usually makes no difference, but it's worth keeping in mind.
Steves DopTest tool is another way to see the command line that Opus has generated, and doesn't require the button be changed to DOS Batch mode.