I've been reading this site without subscription for years, and the bad conscience is slowly getting to me. If you had added a more convenient way to pay for a subscription, like Google Checkout or Amazon, I would have been a subscriber already. You might want to cater more to your more lazy readers...
A Google +1 button for articles would be nice, for those of us who has already sold our privacy to Google for freebies. I'm sure other people would appreciate a way to turn it off (or default off), though.