WPS looks great at first glance and makes a wireless printer connection easy and sometimes is the ONLY way to do so :sigh:
HOWEVER, WPS also creates an encryption key that is just impossible for other wifi users to implement.
The solution I've used is to FIRST setup the SSID and the encryption choice manually BEFORE installing the WiFi printer. Get at least one wifi device to correctly find and connect to your new SSID. THEN install the WiFi printer and when it ask "Is this your first connection?" reply NO. The instructions will seem strange (it will ask to be wired via USB), but it will work correctly if you take your time. This will result in a WiFi key your users can actually use and a wifi printer that will be network accessible as well.