While I regard DDoS as negatives for the web, I think this one was good for Steemers, and even for Steemit, as you point out it shows what needs to be done to grow.
My fear, particularly if SMTs sell like hotcakes, is that Steemit will just (continue to) be neglected to death. I have noted many user suggestions that seem to have not even been noticed by Stinc, and I don't think that's a good thing. Even bad ideas should be addressed, so that people that had bad ideas can find out why they were bad, and maybe come up with good ones.
Overall, my worst concern at the moment is the vulnerability of the witnesses to simply being replaced in a VP based Sybil attack, where Zuckerberg or someone just buys a bunch of Steem and votes in corrupted witnesses, and takes over Steemit.
The only way I can think of to mitigate this vector is to weight VP with something besides SP, or nothing at all. Should SMTs prove a valuable business, the incentive to takeover Steemit will grow stronger, thus increasing the danger of that happening.