Upon running several benchmark tests, he then had several benchmark tests accomplished to see if there was any relative performance drop by comparing the handset on its own, the handset with a case, and the handset with foil inside the case. Results point to the relative performance drop using foil being lower than not having the foil, while others have also claimed similar performance benefits not with a kitchen foil, but through the use of copper foil.
Now this is an ingenious, off the shelf DIY method that will ultimately result in better performance, although chances are you would not be able to take advantage of NFC capability after keeping your handset wrapped with a generous amount of kitchen foil. That should not be too much of an issue, really.