Again, I would exercise caution here.
As AnonymousCoward points out, MS have probably been taking logs of IP vs account vs serial number - and could start banning accounts.
I'm sure MS realised that people would successfully manage to change the serial number and get onto Live. Perhaps we can expect a new "Update" from them soon. What we need to ensure (and someone probably has already done this) is that the XBLive does not store a copy of your EEPROM for later inspection by an "update" - we really NEED to ensure this is not the case. Otherwise this is just a timebomb - and I'm sure that this time your ACCOUNT would be banned.
Other than that, respect due.