Maybe your neighbor can no longer leach your wireless signals.
WPS is a feature for lazy people. All it does is allow you to not key in a password. It has massive security holes in it and should have been removed from all router since it can not be fixed but then lazy people would not buy routers I guess.
It really should not have affected your connection speed. Make sure you did not also disable the WPA/WPA2 which is the actual encryption. If you have encryption on then you should leave the WPS off.