This is why I wouldn't really use anything unless it came from a well known source/developer. Although I don't have 3.55 myself, I'll give you all a warning. Stay calm and don't download anything UNTILL a known dev has confirmed it working universally. We've waited 2 years or so, I think we can wait a bit more. Patience is a virtue. Hopefully this will get developed onto something we can all use. However I doubt it will be a simple .pup that will do the trick. We would need hardware because each system has it's own key, unless we can crack the Algorithm, then I know for a fact we would need some hardware. (I'm talking about people above 3.56 not 3.55). Also I hope this would lead us back to the developer servers, I really miss them lol.
Hopefully there won't be a 4.21 cfw, then all these kids come back to mw2 and host "Redotzity 1337 patch duh :dumb "
We, that actually bought a 3.55 ps3 should have a jailbroken ps3, not all these kids "I poor plz 4.21/4.25 cfw plz i want cllz"

I hope the "Public" keys gets cracked for 4.21 so we'll be able to run games up to 4.21

That would've been awsome. There is probably not going to be a fully functional cfw that installs on 4.21. Hopefully not.