Does the author expect the service to stay free and also remove the p2p features that make it work? Okay, yeah, sort of because he wants to be able to limit bandwidth. But not really. Rather than complaining about upstream traffic, he complains that Spotify should make the non-monetary costs clear upfront.
This is the point of the post - there is a cost to "free" as we all know, and here is one good example. There's nothing wrong if a service is p2p, it should just tell you. Barring that, users of any "free" service ought to keep in mind that it might cost them in other ways.
You're paying for other features... let's say the cost of Spotify not being P2P increases the price by N dollars per month. The "free" users pay N, paying customers pay $5+N or $10+N. I think it's different to complain that they don't offer a "non-discounted" payment plan to opt out of P2P.