Unix Command - watch

I'm sitting here waiting for a huge rsync to complete over a slow network from slow disks to what I hope are faster disks.  To monitor the progress, I'm using the Unix watch command to periodically run a du on the directory being written to.  This gives me an idea of its growth and how far along I am:

watch --interval=1 du -sm /hudson

The -sm options to du just tell it to summarize the size in MB.