Like Donglehater, can't really see the point of staying on 4.21 now that games have appeared that need higher firmware meaning updates won't work and neither will PSN for those games that have updates.
Obviously updates can be fixed, but then it's a big faff messing around doing that again and when you don't really need to...why bother.
I suppose people will be sticking with 4.21 REX purely because it's made by the people behind Rebug 3.55 and they are respected (at least in making firmware
). Is that a reason to stay with it? Not really, it's just doing something because it's "safe" and "known".
Like buying branded malt vinegar, kinda pointless.