Re: Bitcoin XT has code which downloads your IP address to facilitate blacklisting
No, it doesn't. Any miner can create a full block by generating their own transactions for free.
Yup! And they will getting blocks orphaned all the way 
https://tradeblock.com/blog/bitcoin-network-capacity-analysis-part-6-data-propagation
Quote
Next, we examine the size of confirmed blocks that were involved in an orphan race relative to period averages. The chart below suggests that blocks in an orphan race are, on average, ~100kb / 20% larger than regular blocks that are not part of such races. This is likely the result of larger blocks taking longer to relay.
I'm sure that it will be full of miners that love to wasting energy/money.