I have iP3G and iP4. Both have been Jailbroken, restored, and then re-Jailbroken. The iP4 restore and re-Jailbreaking was quite an ordeal! A dedicated iP4 Jailbreak sub-Forum within the "Jailbreak / Downgrading / Upgrading" Forum would have saved many hours of searching.
If there is anyone else out there with iP4 specific restore and jailbreak problems, I'd be happy to share all of the steps I went through to finally re-Jailbreak my iP4. I don't have the wealth of knowledge that a lot of MMi members have, but I could probably explain things in easy to understand terms for those experiencing problems similar to mine.
I don't see the point of that. The jailbreak method for the new bootrom 3GS and the iPhone 4 are now the exact same. SHSH back-up files apply to all newer iDevices. Jailbreak problems are generally universal. All other models of iPhone don't have jailbreak problems b/c they all have the 24kpwn exploit.
You don't see the point because of your level of expertise. Think about all the iP4 users who have no idea what you were describing in your post. I just think it may avoid a lot of confusion and unnecessary posts asking if JB/restore processes are the same for 3GS and iP4.