I forgot he released those in that format, and you're right; he really hit some impressive numbers with that experiment: "A week after the album's release, the official Nine Inch Nails site reported over 750,000 purchase and download transactions, amassing over $1.6 million in sales." (Ghosts I-IV)
I bought both Ghosts I-IV and The Slip. I also spent $300 on the Girl with the Dragon Tattoo soundtrack that he put out last week.
And I downloaded Niggy Tardust for free. I did this because I had never heard Saul Williams and wanted to support an artist who I had never heard of. But after listening to it, I honestly just didn't like it, so I did not go back and buy it.
I wonder how many people were like me and downloaded it for free because of the experiment and Trent Reznor's involvement but didn't pay because it wasn't their style of music.