We have used UCX tool in January-2024 and was more of an assessment tool. Event today it's not a tool that one can "unleash" in their environment to perform a migration. For one UCX still doesn't have notebook migrations. If you are using RDD, DBFS, or APIs in notebooks - you're pretty much out of luck with easy UC migrations.
Other issues:
Migration is a cost: both people and data movement cost (AWS + Databricks' multipurpose clusters)
Testing is a cost: people, plus one have to run 2 parallel environments (AWS + Databricks costs) to ensure that everything works ... or take a tremendous risk plunging their entire environment into UC.
3 part names. This can be mitigated by using default catalog, but that requires testing as well ... or forcing all your customers to rewrite their queries.
