As for rooting, it was said earlier that rooting does not wipe your phone. For those folks who are saying that, have you read the instructions for rooting a GNex? To root it you unlock the bootloader which wipes your phone as clearly stated in the instructions. The DX's root method didn't but that appears to have no bearing on the GNex.
At this time, I couldn't care less about unlocking my bootloader. I'm getting the first ICS phone for a reason and don't see loading ROMs as compatible with experiencing ICS. I DO want to root it so I can do proper backups with TiBackup and tweak the little things root provides. I also assume Windbag's tweaks require root.
Seems like a good strategy is to mess with the phone for a bit to ensure it's for you, knowing anthing you do is temporary. As soon as you know it's a keeper, root that pig, thus wiping the phone THEN start installing and tweaking with gusto!
At least that's the strategy I'm planning on using,