[TIP] Downgrading from 3.0 beta 4 to 2.2.1 OS X
So these standard steps still work for the most part
1. DFU mode (NOT recovery mode)
2. Restore to vanilla 2.2.1 (get 1015 error)
3. Download and extract iRecovery. This is a console app to be run in terminal. Extract it with finder.
Copy libusb-0.1.4.dylib to /usr/local/lib and chmod both iRecovery and the dylib to 755 using chmod 755 /usr/local/lib/libusb-0.1.4.dylib and chmod 755 iRecovery.
In terminal, run iRecovery -s
At the iRecovery prompt, type: fsboot
Wait, iPhone should boot. If not, type fsboot a second time.
ctrl-c or close the term. You are done with iRecovery.
after this your phone should work. (thanks to mocque for the iRecovery tip)
4. DFU mode (NOT recovery mode)
5. restore to pwned 2.2.1 ipsw
however, iRecovery gets a bus error with the new components installed with iTunes 8.2 beta 2, my solution was to use another computer that still had the older version of itunes for the iRecovery step, i also used QuickPwn to pwn it afterwards on the other computer because after rebooting it would put me back in restore mode, once pwned i was in 2.2.1 without any issue. had a little annoying experience that im sure anyone else who decides to go back (For whatever reason) can use the experience.