In my anecdotal experience it's been sort of terrible from the start. In my first interaction with it, it suggested that I use a library that had been deprecated for a few years, which is when I found out it's data cut-off point was in 2021.
We've been building an API with: Asp.Versioning, Microsoft.AspNetCore.OData.Query,, Microsoft.AspNetCore.OData.Deltas and Microsoft.EntityFrameworkCore, and it's been very bad at it. I think it's sort of understandable, because there isn't a lot of documentation or examples for these libraries, and, some of them have changed a lot since 2021, but it can't even write an ActionResult function correctly without a lot of help. At one point we asked it to do something resulting in some very terrible code. When I pointed out what was wrong, it apologized and then proceded to give me the exact same piece of code.
We use it quite a lot, along with co-pilot to test the waters, and so far it's rather unimpressive. From my completely anecdotal experience, it hasn't gotten worse, but neither are useful for things that haven't been solved a million times before. I think the major advantages we're going to see from it is in terms of automated documentation and possibly having it write tests.
That being said, I don't think it's that much worse than google programming. C# documentation is really hard to find. Some of the Odata documentation is a github repository with very few comments and only in-memory example code, but it was easier to find through the use of chatGPT than it was on Google. I do think it needs to automatically include the source and date for what it bases it answers on to help you navigate the answer. What I mean by this is that IActionResult wasn't replaced yet by ActionResult in 2021, so if it simply told you that it's answer is old, then you'd probably be more inclined to look things up in the official documentation. I know I would.