It depends on the task. Oneshotting 80% of the new feature and then failing to pick up on details can leave hard part.
But oneshotting even 30% of UI tests based on QA regression means you have 30% of regression covered. Ofc you need to verify if the test is indeed covering the test case, and for a big volume of tests it takes time, but it's nowhere near what it takes to actually write the tests.
AI analysis of the code flow & AI-assisted debug (placing print statements, reproducing the issue, duping the print into it) transforms some 2-3 day investigations into half a day of work.