I don’t think this “paywall” is a big deal or something.
For individual publishers, it seems you still can use whatever you want to charge your users. Medium did say they will attempt to “filter” and “personalize” stories, they promise that kind of crap for a long time, for basically everyone anyway, pick your annoyance, blah blah, and they are going to roll out new features (so founding members will be like paid beta testers basically);
I recommend membership to my friends, as I did not get the sense of anything “evil” in this call TBH; of this so called “exclusive” features anyway to lock out other people of contents behind paywall or something, I have seen worse, :-)
If my five bucks a month helps Medium keep its flag flying high, yay for that is how I see it.