I've always been of the camp to say, if I have to legally license my dog (who is a sweetie and not dangerous in the least), you should legally have o register your gun (or guns)... simple as that.
Of course the NRA will posit the argument that a registry would provide a list wherein the government could come and take your gun, but with the 2nd Amendment protection in place, that really is a fallacious argument.
I heard someone on NPR here in DC actually make the argument that the Heller decision, having established that there is an individual right, will actually make it more difficult for groups like the NRA to argue against registration.... because now the government can't legally take away your gun.
I'm all for 100% registration. To be honest, I'm all for laws requiring trigger locks. But I think the individual right in and of itself is good, and SCOTUS was right to uphold it.
If gun ownership is an individual right then government must be very circumspect in regulating it. That is Scalia's argument in his first paragraph. Scalia's opinion gives the NRA very powerful ammunition against gun registration, arguing otherwise is absurd.