Is SQLT safe to run in production?
This is from the sqlt instruction file itself:

"For statements that modify data, i.e. INSERT/UPDATE/DELETE, a savepoint is created prior to statement execution and the transaction is rolled back to the savepoint at the conclusion of the session. For further information regarding SAVEPOINT please consult the Oracle Concepts reference manual".

This means if you are using XECUTE method, the data it inserted during execution will be rolled back at the end of execution.
If you are running this in a production system with thousands of transactions per second, you might want to consider the additional load this insert/rollback will put on the system.

Hope this helps :)