It can work.. actually at least it used to work often. I would not recommend using UPnP though, if you know how to forward a port, since that is fullproof and UPnP is not.

I have tried it on 3 different routers over time and all of them worked using UPnP, but only one of them actually got the brick wall to disappear completely. On another one, I always had the wall and on the third one, I guess it depended on the mood the router and/or Limewire was in.