It went from 10 uses in England and Wales in 1998 to 48 uses in 2008, so I think it is becoming slightly more popular here, fitting in with the 'old names' trend. But I'd be very surprised if it made the top 100, unless it's used by a celebrity or on a very popular character in a book or film. People seem to find the Ag-syllable ugly, and the saint connection doesn't help: googling images of St
Agatha is seriously unpleasant business!
I personally love it. But, like RowenaRavenclaw said - name nerds do.