When I updated to 1.0.0.1, I opened my creative world and went to the end and was met with massive lag. Near the end portal (having killed the dragon multiple times) was a fountain of torches spewing out of the torch blocks with the bedrock of the portal flickering. For some reason the bedrock was breaking itself dropping the torches then regenerating.
I am unsure how to reproduce. I would expect this not to happen as this also lags the over world as the torches travel back through the protal creating a massive lag zone.
The screenshots below show the torches and what happened after I typed /kill @e to get rid of the lag.