Well, after a few hours and several different Google searches, my iPhone 3G is now jailbroken and has Whited00r on it. I think my phone may be the fastest it’s ever been, and I’ve tried iOS 3.1.3, 4.0, and briefly tonight 4.2.1 on it. I updated my iPad to iOS 5 tonight and, on a whim, decided my aging iPhone could use some more flash and glitter, too. Someone on Reddit mentioned Whited00r as being a way to make your older iPhone speedier while still getting some of the features from later iOS versions, so I decided to try it.
It was kind of a hassle at first, since just restoring to the Whited00r IPSW didn’t work: I got error 1604 from iTunes. Reading online, it looked like installing Whited00r on a jailbroken phone had fewer problems, so I figured I should jailbreak it first. I’ve never jailbroken my phone before, so finding the right version of the right jailbreak tool for the right OS took some hunting. It didn’t help that Whited00r left my phone in some unusable state, so I tried to wipe it back to 3.1.3 but that failed. The only way I could get a clean starting point from which to jailbreak was to allow iTunes to restore my phone and update it at the same time, pushing it to iOS 4.2.1. I think what finally worked for me was Redsn0w 0.9.6b4 run on my Mac, though it took a few attempts to get into DFU mode. A few forum posts about having trouble getting into DFU mode specifically on a 3G running 4.2.1 made me panic a bit about being able to do it, but it finally worked.
After jailbreaking my phone, I was able to restore through iTunes to the Whited00r ISPW. When my phone booted back up, it didn’t want to leave the unlock/emergency-call screen, and I hit the home button too soon apparently and interrupted its activation process. The screen was a weird cross between the recovery mode background image and the slide-to-unlock bar. It gave an error about failing to activate, try again later. I unplugged the phone from my Mac and replugged it. I think it rebooted again at this point, too. When it came back up, I left it alone and it magically activated itself and then I had the usual unlock screen.
I’ve been syncing all my crap to it since, and from the little I’ve played around with it, it’s pretty snappy. I have the snazzy desktop wallpaper capability, folders, and video recording, that I’ve discovered so far. I’m also looking into what apps Cydia provides that I haven’t been able to get before.