Is there a way to return "Drupal root" value that is faster than running drush status?
cd /path/to/drupalroot/sites/default
drush drupal-directory '%root'


On the old system I'm on right now, that clocks in at 3.5s, vs. 11.8s for drush status

If you are using site aliases, as tenken suggested, then you can do this:

drush sa --format=csv --fields=root