From their FAQ: "How compatible is Mojo with Python really? Mojo already supports many core features of Python including async/await, error handling, variadics, etc, but… it is still very early and missing many features - so today it isn’t very compatible. Mojo doesn’t even support classes yet!".
Overall, pure Python seems to be about 100x slower than what you can reasonably get with a compiled language and some hard work. It's about 10x slower than what you can get from JITs like Pypy and Javascript, when such comparisons makes sense.
I agree that Mojo remind me of Cython, but with more marketing and less compatibility with Python. Cython aspired to be a nearly 99% superset of Python, at least that's exactly what I pushed my postdocs and graduate students to make it be back in 2009 (e.g., there were weeks of Robert Bradshaw and Craig Citro pushing each other to get closures to fully work). Mojo seems to be a similar modern idea for doing the same sort of thing. It could be great for the ecosystem; time will tell. Cython could still also improve a lot too -- there is a major new 3.0 release just around the corner!: https://pypi.org/project/Cython/#history
Overall, pure Python seems to be about 100x slower than what you can reasonably get with a compiled language and some hard work. It's about 10x slower than what you can get from JITs like Pypy and Javascript, when such comparisons makes sense.
I agree that Mojo remind me of Cython, but with more marketing and less compatibility with Python. Cython aspired to be a nearly 99% superset of Python, at least that's exactly what I pushed my postdocs and graduate students to make it be back in 2009 (e.g., there were weeks of Robert Bradshaw and Craig Citro pushing each other to get closures to fully work). Mojo seems to be a similar modern idea for doing the same sort of thing. It could be great for the ecosystem; time will tell. Cython could still also improve a lot too -- there is a major new 3.0 release just around the corner!: https://pypi.org/project/Cython/#history