Because of the way I learned music, though I could play from the dots, I didn't know the names of the notes. We had been taught the "FACE" and "Every good boy" and that stuff when I did the few lessons when I was small, but I couldn't relate them to the music without stopping to think about it, and the notes on the recorder were just notes, not names. In recent years I've learned the names, though it sometimes does take me a second or two, if someone says "Give me an A" to work out where that is. I think it would be fair to say that I have found it useful to know the names and now that I'm progressing further with the musical knowledge I think it is beginning to become necessary not just useful.

I guess it depends on how far and in what direction you want to take your musical knowledge.

Love Lynne