Any improvement to the ChatGPT free plan is really nice. It's easy to forget that most people have never used a SOTA model, and only think of their experience with GPT-4o or Google Search's AI Overviews when asked about AI.
Terra is far from awful. I've not used Luna enough to judge whether it's significantly better than Luna, but at least via GitHub Copilot, Terra is leaps ahead of Sonnet 5.
It used to be 10 messages every 5 hours using GPT-5, then unlimited 4o-mini. More recently, it went down to ~5 messages per day on 5.5 Instant, then unlimited on 5.5 mini.