Your perception and inference are both wrong. App.net isn't just going up against twitter, but rather the entire social networking paradigm where I have multiple signups and not enough use. If we use app.net to login to most major services and post, like I have to do with twitter, facebook and linkedin right now, I get away with a single login.
What'll drive adoption? The developer incentive program. This also answers your John Deere example... There will be a lot of offsprings from App.net. In a rudimentary tone - a fb-clone, an instagram clone, comments systems (bit.ly/qbdebut)etc...
I talked about Twitter specifically because the OP talked about Twitter specifically.
I don't doubt that there will be lots of offsprings from app.net, I'm just dubious about whether they'll gain any traction. "You only have to use one username/password!" isn't enough to get people to spend $5 a month.
I don't think that app.net is selling an identity service that will take off or be worthwhile, but I strenuously disagree with the assertion that people won't pay for single sign in on the Internet.
It is, in my opinion, the number one pain point on the web today. It affects users of all technical levels and the more you have invested in the web the worse it gets.
Ah, single sign-in... also offered by Twitter, Facebook, Google, Firefox, my email address...
I don't disagree that people might pay for it, but why would it by App.net I'd pay? Why would they even pay though? You can trust the App.net developers? No more than those listed, realistically.
What'll drive adoption? The developer incentive program. This also answers your John Deere example... There will be a lot of offsprings from App.net. In a rudimentary tone - a fb-clone, an instagram clone, comments systems (bit.ly/qbdebut)etc...