Hotz announced his quick success on his blog. "It's not any sort of version string change; I would have added something showing off the new features of 3.21, but oh wait, there aren't any," he writes, "This can be installed without having to open up your PS3, just by restoring a custom generated PUP file, but only from 3.15 or previous."
Hotz believes - but he's not sure yet until he can try it out - that this firmware update will even enable the "Install other OS" feature on PlayStation 3 Slim models. This is pretty cool, since that model never had the feature in the first place.
What goes around comes around, Sony. You remove advertised features - hackers will find a way to get it back. "Note to the people who removed OtherOS, you are potentially turning 100000+ legit users into 'hackers'," he added, "There was a huge (20x) traffic spike to this blog after the announcement of 3.21. If I had ads on this site I guess I'd be thanking you."