How is it different from Open Transactions with Smart Contracts?
Not familiar with OT and their Smart Contracts. However, Ripple's proposal is using a secure sandbox that allows you to write in any programming language you please, is a very good move from practical stand point.
Also, not sure if OT allows Smart Contracts to run offline by Smart Oracles. There are some really good pieces in this whitepaper and I would love to see what Bitshares is planning for Smart Contracts.
I'm not a huge fan of the Bitcoin scripting and escrow as it currently stands. We need something more innovative and easier for developers to get involved. What Ripple's whitepaper proposes I think is a step in the right direction.