My problem with App.net is that the user payment is only a means to an end no one has explained yet.
I welcome any competition to Twitter to make them step up their game, though, so from a spectator's view, I couldn't be happier to see App.net succeed. As a hypothetical user, the platform holds no appeal to me. I still remember Jaiku, Pownce and Identi.ca.
I guess my only quibble about App.net is that I've never personally seen the appeal of the micro-blogging/twitter social model. I don't like to "follow" people, and I like to say things to other people in more than 140/256 charters. I believe that there is a generally correlation between the length of people's comments/text and their quality.
I would like to see a more integrated real time feed, i.e the music people listen to, the movies they watch, where they eat so that developers can use it to make recommendations to me. That would be awesome as long as I can have fine grained control over who get access to what information.
I am excited to see if App.net is going to go in this direction.