New versions of buildkit are likely to include new versions of tools. The new tools will download automatically when you first run "civibuild". If you prefer to download explicitly, then re-run "civi-download-tools".
In version v14.05 (and earlier), each build included two databases: one CMS database and one Civi database. If you ran unit-tests in v14.05, the tests would reset the Civi database -- which was problematic if you like to alternate rapidly between unit-testing and manual testing (because any manual DB changes are lost).
v14.06 addresses this by provisioning a third database for testing. This requires some changes -- eg creating the database, saving the metadata (eg "build/drupal-demo.sh"), and updating configs files (eg "build/drupal-demo/sites/all/modules/civicrm/tests/phpunit/CiviTest/civicrm.settings.dist.php"). You can fix all of this by reinstalling the build (which will recreate all databases and config files). If the build is named "drupal-demo", then simply run:
civibuild reinstall drupal-demo