Are there any pitfalls pointing config sync to profile's config/install? Is this good practice? I have pointed my config sync to:

$config_directories['sync'] = 'profiles/PROFILENAME/config/install';


Experiments with drush cex have worked, allowing a cycle of UI changes, config export, and re-installation with the new changes.

We will not be going live with D8 for a while, so the team's plan is to use this method to gain familiarity with the config system and other parts of D8 using this simple method.
No, I don't think that is a good idea. default configuration is something else than the config sync folder. For example exported config has a UUID and system.site has a site UUID while default config shouldn't.

They are two different use cases. default config is for installing new sites and the config export is to deploy configuration between different installations of the same site.

What you might want to look into is https://www.drupal.org/project/config_installer, a simple installer that allows to install based on an config export/sync folder.