I think Honda switched to a new synthetic ATF this year... it used to be ATF-Z1, but there's a new one now, I believe it's ATF DW-1 which is supposed to be backwards compatible.
Edit: found a bulletin online: http://www.handa-accessories.com/dw1.pdf
Yes, the previous Z1 did not work well with some parts/seals so Honda finally switched to new DW-1. I know many have gone with Amsoil ATF and are happy.
Now, is the DW-1 synthetic?