GPT is super prone to error on any niche thing, be it subtle nuance or concrete details, but i don't actually find it to be any more or less reliable to the state of the web. Ie most content i consume from the web is full of errors, incorrect facts, etc. I don't find my suspicion of this to be any different than that of GPT. However GPT has a great way of having the relationships to error-ridden results in the web already established. I can ask it about this web of things to get a better understanding when i drill into concrete facts via standard search.
GPT is far from a gimmick in my usage, but i also don't think it's revolutionary yet. I use it because i'm exploring and finding it useful, but also because each new leap OpenAI makes is pretty damn impressive. This week they're rolling out Plugins i believe. Every step they take is fun to be with, fun to use, fun to experience. That alone is worth the $20/m for me.
If I forget some api or technique in some language, I ask it. Depending on its results, I may or may not start browsing for more details or to verify.