I am sarah on github
Which feels rather like buying coke.com back in 1999.
I have never been sarah on anything: it's always taken. I've been sarahg3, sarahg.gray (which I am quite attached to, so this one's not a compromise), sgray, and any other combinations of my name, initials, and various secret numbers (such as the highly secret number, "3").
I feel it's a momentous occasion, in a small, quiet way. Getting to be yourself and not just your concatenation.