[IanCal]

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.