One of the hardest issues of migrating content from legacy system(s) into a new Drupal site is that the new site is constantly changing while it is under development.

A day doesn't go by that someone isn't asking a question in Slack #migration about how to troubleshoot a specific problem with a tricky migration.

If you are weighing whether to upgrade to Drupal 8 but aren’t sure what kind of budget to expect, we’re going to breakdown the upgrade (migration) process. Along the way, we'll highlight the factors that will add hours to your project.

One of the things I constantly get asked about in the Drupal 8 migrate space is when will migrate be ready for use. With the API being marked stable in 8.5.0, now is a good time to consider upgrading. Upgrading a D6 or D7 site should be ready, especially if you have mainly core modules in use.

Today, the final blocker for Migrate Drupal UI was committed. That leaves only a series of complicated internationalization (i18n) issues to get resolved for Migrate Drupal before all of migrate in all of Drupal core can be considered stable.