With this model, we feel that projects like colored coins and metacoins like disastercoin will have a much easier time building on top of Ethereum than Bitcoin.
I'm afraid you're missing the point of colored coins and disastercoin: they are supposed to extend functionality of Bitcoin.
Obviously, smart property, user currencies and decentralized exchanges can be implemented in a variety of ways, but there is a significant demand for things like this specifically from Bitcoin community: people who already own bitcoins and want to trade using bitcoins.
Decentralized exchange/smart property applications on top of Ethereum might be awesome, but it's not same thing as colored coins and matercoin.
Yes, any alternate option of starting their own blockchain is avoided - because it would undermine their co-opting of Bitcoin's hash-power. That's the key, using other people's resources instead of having an opt-in system. You know, just like the existing financial system does. Combining that with their escrow "peg" that should just "work", it seems that the only thing they're replicating is legacy centralization tendencies found in fiat systems.
But of course, they don't see it that way, all that hashing-power is for their use! No "ifs", "ands" or "buts"! Heresy to anyone suggesting otherwise!
The cat is out of the bag, and these guys don't understand that there are better funded players nipping at their heels that don't pull the dirty tricks they are to get the functionality needed. Should be fun to watch the deployment, It'll answer the question "What if we built something and got lapped by someone else?".