We have tried out Gemini code review vs Copilot code review and Gemini is consistently offering better code review tips. It has officially caught multiple potential bugs, even a few that reviewers might have missed, so it's definitely been additive.
Observability looks way worse. Github Agent has a full UX built into the Github PR that lets you dig into the agent behavior. This requires you to egress text logs and make sense of it yourself.
Also curious about customization. Github just rolled out "agent writes its own instructions" https://github.blog/changelog/2025-08-06-copilot-coding-agen... which is super cool, how do I customize this one and teach it how to start and manage apps across my monorepo?