Sweet that they are replacing older adapters too. My PGB4 adapter has had electrical tape on the connector for a ling time, since the insulation has frayed.
I have a bad MB adapter too, so I will take both of them in for free replacements!
Be prepared to bring in a copy of the Tech Note for this issue. I went to the local Apple store today with a MB Adapter, and a PBG4 adapter. The insulation on the MB adapter had separated, and started to melt. The PBG4 strain reliev had cracked, and the wires were exposed.
The Genius Bar had not heard of the Tech notes - even though I pasted them into the "anything else we should know" section of the reservation form for making a Genius Appointment.
They wanted me to bring in the computers - even though the tech note said that wasn't necessary. A second genius came over and said she HAD read those Tech Notes (from my reservation), and said "they were legit". The first Genius seems quite distraught that Apple was not requiring the S/N of the computer.
The first Genius had been arguing with me, and I don't think he would have helped me, had he not spoken to the 2nd Genius.
In the end, they swapped the MB adapter w/o incident, although they REALLY wanted the computer S/N, so I gave them my Apple ID and they looked it up.
I struck out on the PBG4 adapter. Evidently he felt that my "broken strain relief" was not the same thing as a "separation of the cable at the strain relief".
He did offer to so a out of warranty repair (ie replacement) of the adapter for $60 (instead of $80 for a new one). I told him it wasn't worth it. I have another dead one at home, and I will just replace the cables. it may be a bit ghetto, but for my plod PB it will be fine...
So - just a heads up to go in prepared, and be ready to educate the Genius, because they may not aware of this issue. I would take your computer S/N also.