Before it was free for limited features, pay for all features. Now it's free for all features. If you pay $2/month you're supporting the site and the ads go away.
I use reminders and recurring tasks a lot now. Before, people using the free version didn't have access to them which I think is the coolest part of the app.
I dug this up as im curious to know:
What it was costing to use the site before?
What the plan is to support the site, now that it is free (the experiment)?
From that link, there is some great feedback. http://news.ycombinator.com/item?id=2442724