So who's used Pwnage to upgrade unlocked iP4?

I have an iPhone 4 running 4.0.2 thats unlocked. It only has files saved for 4.2.1 so I was thinking of using pwnage to upgrade to 4.2.1 but I've heard of several people getting no service after upgrading using pwnage. I don't want this to happen obviously because then I'm stuck with an unusable phone. Who's tried it and had it worked and if it didn't work, did you figure it out so you could restore service? Thanks!

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