I think it is accurate to say that we dismantled international terrorist organizations to the point where they wouldn't be capable of conducting a large scale attack on U.S. soil. In that sense mission accomplished, now we only have to worry about "lone wolf" type missions conducted by individuals exposed to too much propaganda, not well funded full time terrorist cells like Bin Laden.
As Charai said, the costs, in terms of lives and money have been incredibly high, Pyrrhic victory.