It definitely depends heavily on how well represented the subject is on the internet at large. Pretty much every question I've asked it about SystemVerilog it gets wrong, but it can be very helpful about quite complex things about random C questions, for example why I might get undefined symbol errors with `inline` functions in C but only in debug mode.

On the other hand it told me you can't execute programs when evaluating a Makefile and you trivially can. It's very hit and miss. When it misses it's rather frustrating. When it hits it can save you literally hours.