A's Ballpark Pass?

I got a marketing e-mail from the A's today advertising a "Ballpark Pass" which grants access to every single home game for $19.99/month. Has anyone signed up for this? It seems too good to be true. What's the catch? I assume you get the crappiest seats available but it's still a great price because even 20 bucks is better than most terrible seats and even if you only go to a few games a month you get your money back...