I think that Erik and his team are agile enough that a feature war is not a problem.
All a competitor would do is prove the market for the next shiny addon,
...much like everyone claims someone can (and people do) copy SD, SD can easily implement new features the userbase wants.
The bitcoin gambling arena is going to be just like the soda wars -that with the biggest billboard wins.
& much like coke is integrated into mcdonalds, SD is integrated into
https://blockchain.info/wallet/SD is also mentioned in nearly every article written about Bitcoin ... that is valuable. jmho
Bankroll + brand awareness(trust) = satoshiDICE for the win