Difficulty futures? What?
Are you also going to buy credit default swaps to cover in case these diff futures don't actually pay out?
If you want to hedge against difficulty, sell your mining stocks.
We offer the same futures on Bitfunder since February and they were always paid out on time (regardless if at loss - already happened), as well as customers of CoinBr.com MPEx brokerage got all their withdrawals. CoinBr users were also among first ones when SatoshiDICE paid out, mind you that such an unexpected big event would cause any naked scam to fold.
And thanks davos for the explanation, you are correct.