First impressions with this is they give really long estimates.
Also, due to coding agents, you can have them completely implement several different approaches and find a lot of unknown unknowns up front.
I was building a mobile app and couldn’t figure out whether I wanted to do two native apps or one RN/Expo app. I had two different agents do each one fully vibe coded and then tell me all the issues they hit (specific to my app, not general differences). Helped a ton.
I asked it to estimate a timeline for a feature in my hobby project and it confidently replied, “4.5 weeks to code completion”.
Less than 4 hours later, the feature was done. I asked it to compare this against its initial estimate and it replied, “Right on schedule!”
I have completely given up on using it to estimate anything that actually matters.