No it doesn't "understand what I'm doing" or "get everything right" but that's hardly the point
It's often reducing the amount of labor I'm doing by hitting the keyboard by guessing 90% correctly what I was going to type
It also often saves me from having to google how to do something, it's effectively serving me a search result right along my code
I'm lucky to be getting it for free but would have immediately paid $10. It needs to only save you minutes a month for that to be worth it
Also the comments about it being "unfair their monetizing other people's work" are missing the point.
Github has created a product that many people use and through that effort created a large repository of code.
They are now releasing a product that is going to create a large amount of of value in time saved and are maybe capturing 2% of that. This is a great outcome for everyone