HDD Decryption is the very actual topic in the PS3 Scene, but what do you expect of it? A custom firmware + isoloader and choco cookies? The bad truth is that, this "hack" only removed the HDD layer encryption, but not the file encryption itself. Means: You get a few sprx, rco and xml files, possible a few more types but those are useless unless you can remove the encryption of the file itself. But you can't yet. So the only thing you can do for example is getting the firmware part which is on the HDD. But these are only UNPACKED files, NOT DECRYPTED files. You may be able to replace several firmware files ye, so if replacing some text in the XMB or an icon is a custom firmware for you, have fun with the knowledge that this may brick your PS3 and is useless as hell.
If you now ask me if this hack is even true, I would say yes. There were several very unknown (but public in some forums) HDD decryption methods in the first PS3 days which worked aswell, so why not on the new firmware...