I wish I'd seen this when it was originally asked, but for future reference, I've been using Your Member
for a year now at my site, Good Life Menus
. I have a weekly gluten-free menu service. Every week, I post a new menu, and I want only members to be able to access the menus. Your Member makes it easy for me to have people subscribe and pay. It automates everything for me and has a lot of functionality I haven't even accessed yet. It also has a tag you can put in so that you can make teaser excerpts; it allows for coupons, pay per post, subscriptions, and more, and several levels of membership so you can make any page or post accessible to only the categories of member you designate.
In addition, the support is great! There's good documentations, an active forum, and the developers are very responsive to the customers. It's not a free plug-in, but worth every cent.
I should mention I'm not affiliated with them and not paid to say this. Just a happy customer who came here to solve a problem I'm having when I upgraded Atahualpa, and started browsing the forums.