Partly out of curiosity, but it also might help get an accurate answer - what kind of work are you doing?
I think I'll be able to call myself a full-stack developer in a few years time but for now I'm happy to be called just a RoR web developer.
I had once worked with a senior colleague who would run process traces on the live Oracle database and uncover bugs in Oracle's code. I am at the level where I can find bugs in open source code bases about which I've no idea but not where I can find bugs only with the binary.
Then again, I see so many comments on HN about which I've no idea and which still seem relevant to what I do.
So, you see where I am right now.