minmal differences so far. I just upgraded to 4.2(greenposi0n) from 4.1(limera1n)
i don't unlock
i synced with itunes and then updated through itunes to 4.2.
device was stuck in restore loop as itunes would error (1033) near the end of the recovery process after 4 attempts. TinyUmbrella would fail to kick device out of recovery
I ran greenposi0n and it JB and kicked the device out of the restore loop and I was able to complete activation through itunes afterwards.
after activation I was then able to restore from my last sync (or back up) and regained all my photos, contacts, and apps.
Only problem I seem to be having is that the lockscreen and homescreen are darkened only on the bottom 1/4 of the screen and iwipecache and reboots will not clear it up...