I bricked my 3gs yesterday trying to do the 1/2 siri port. the iPhone 4's N90AP.plist file text is not compatible with the 3GS N88AP.plist file required to write the siri gui code. I restored my 3GS and re-untethered jailbroke it (also noticed you can tether an untetherable device with the new redsnow)
jailbreak, ifile, iphone explorer for mac, look it up on youtube. you will have siri (kind of). check out my youtube video of how I got siri on my iphone 4
Of course it's tethered cause dev team slacking on the untethered for iPhone 4! Whats coming out is the untethered for iPhone 4s and iPad 2!!! Hmmm didn't I say that weeks ago and people said "you don't know what the your talking about"
Untethered will be for all ios5 devices due to the nature these exploits tend to be. Harder to find as well. The focus is always on the newer device for a good reason, so if you have a iphone 4, like me, just be happy to have the option to JB. They are doing this for free and no one has the right to be pissy about it. If you can do better/faster go ahead, thats what GeoHot did, he didnt complain on iClarified