Timing web requests is possible in curl using the -w or --write-out flag. This flag takes a number of different options, including several time based options.
Creating a symlink is a common way of ensuring that the directory structure of a deployment will always be the same. For example you might create a symlink so that the release directory of release123/docroot will instead be just current.
Grep is a really powerful tool for finding things in files. I often use it to scan for plugins in the Drupal codebase or to scan through a CSV or log file for data.
For example, to scan for user centric ViewsFilter plugins in the Drupal core directory use this command (assuming you are relative to the core directory).
Part of the process of putting a new site live can be moving DNS entries around. Prior to doing this it's a really good idea to sort out the Time To Live (TTL) of the DNS record so that when you do change DNS entries you aren't waiting around for a day for the DNS to sort itself out.