A recent study by METR reveals that experienced software developers using AI tools, specifically Cursor, actually face a 19% increase in task completion times rather than the anticipated speedup. Participants initially estimated a 24% time reduction, and post-task beliefs suggested a 20% decrease. Lead authors Joel Becker and Nate Rush expressed surprise, noting that developers often needed to adjust AI suggestions, which, though directionally correct, weren't entirely accurate. This challenges widely held assumptions about AI's productivity benefits in software development.