App.net - It's not a pay for Twitter.
With Twitter, Facebook etc you’re not the customer; the advertisers are the customers — you’re the product.
With app.net, you are the customer.
If that’s your bag, then great. If not, move along.
This small shift in focus makes the way for a much more stable environment for something long lasting and meaningful to be built. Personally I hope it evolves into more of a utility than a service, but only time will tell.