What are you basing how good they are on? Personal experience or some benchmarks?

Benchmarks, we have internal ones testing reasoning fine-tuned v/s frontier + prompts

For some use cases it can be parity performance at 1/20th the cost up to exceeds at 1/10th the cost. Trade-off is ofc narrow applicability

How can I learn more about these models? Are they open source?

there are plenty of OSS finetuned models + base models around. If you're looking for doing these on your own dataset, worth getting in touch with cartesien.io or wire up https://github.com/SalesforceAIResearch/PretrainRL-pipeline

Thank you.