I see I'm too late to the party. The dd command is the ONLY way I've ever been able to successfully burn Arch to usb. The catch-22 is that you need a *nix to use this, and you are needing to do that so you can get a *nix. But, I've never had any luck doing it any other way.
Also, I was able to burn Arch onto a less than 1gb usb drive. Don't know if that matters to you..