Good thoughts. I'll share a couple that seem to be relevant.
Facebook, for all its faults, has done a masterful job of making it really easy for folks to integrate. And it's a very intuitive interface, even for folks who remember MySpace (though I never cared). Notification of what's happening in relation to your account are instantaneous. Until someone comes up with those things, I doubt it'll be replaced.
Is Steemit going to do all that? I don't know. But I kind of don't want it to. Some of the features would be nice, but maybe trying to be a Fb replacement would be short-selling it.
A downfall right now is that there's a lot of noise, there are a lot of very popular people making huge sums because of their followings, there are a ton of very poor articles and a massive amount of great content not getting attention. How will this flesh out? We'll see. Of course, poor writers usually give up. Hopefully people will wisen up on not cheapen the Steamit brand by voting for people just because they're popular, forcing them to produce some good content. It's a maturing process. It'll be interesting to see what Steemit grows up to be.