I'm a recent convert, been experimenting with converting one PL to another.
GPT-3.5 will get the gist of what the code is doing, and then provide what looks like a direct translation but differs in numerous details whilst having a bunch of other problems.
GPT-4 does a correct translation, almost every time.
It kills me that there's a waiting list for the API. I have put together some tools to integrate 3.5 into my workflow and it helps for my current task a lot (for others it's useless). But to really shine it needs to have API access to 4.
I recently finally got access to 4 in the API, it's good. It's much better imo at following the system prompt too. Faster than you see in chatgpt I think, not as fast as 3.5-turbo but definitely less tedious.
My only kind of quantitative answer is that I had 3.5 creating ember templates & data and it would get the templates mostly ok after a couple of iterations of fixing errors, almost never on the first shot (if ever). Often wouldn't quite get it in two, and data structures would often be kinda there but not quite. Required a lot more care with the prompts. 4 gave me working things every time first time (except only where it did things that were fine in a template but not currently supported by the custom framework I'm using them in), and didn't need as much hand holding.
Qualitatively, it's wildly different from gpt-3.5-turbo for discussions. 3.5 feels a little formulaic after a while with some kinds of questions. 4 is much more like talking to an intelligent person. It's not perfect, but I'm flipping between discussing a sporting thing, then medical malpractice, legal issues, technical specifications and it's doing extremely well.
If it's affordable for you, I'd really recommend trying it.
For code 90%+ reduction is easily correct. For text and other content, I can't say, but I would guess it's not that good.
Anything involving reasoning, code, complex logic, GPT-4 is a breakthrough. GPT-3.5 turbo is more than good enough for poetry and the other text generation stuff.
