The impressive thing about GPT 4o is how well it performs at most metrics. GPT 3.5 was already very impressive - most other companies are just catching up now. GPT 4o is a huge step above.
GPT-4o replaced GPT-4, not 3.5, so it’s not “a huge step above” it, at least not subjectively. It is much faster though, so at least it’s got that going.
The voice thing is a potential killer feature though, I can’t wait to try it, and to have my kids use it.
I would argue that the biggest novelty is being able to share your screen or camera feed with the live voice - and there's no announced timeline on that yet at all.