Yes, you do have to buy the zipsets in order, and you cannot buy them all at once, and they're very expensive and the newer ones are VERY explicit.
Is it worth it? If it's worth it to YOU, it's worth it. And if you're planning on waiting until someone shares them on the forums, good luck with that. You won't find any of her newer stuff in any forum, because she protects her newer stuff like you wouldn't believe, and I think the fact that the really explicit stuff is really expensive plays a role in that. If you pay like 29.95 for content, you're probably going to share it, but if you pay hundreds for it, your attitude is going to be, "Why should I let you view it for free when I paid an arm and a leg for it?"
I'm neither defending nor condemning what she does. Just pointing out what she does, and telling you what you probably already know. She protects her content like its pure gold, and it costs almost that much. Gripe all you want, but the fact is her site has been up for years, and for the amount of time that site has been up, there's VERY little of her content in the forums. Whether that's good or bad is dependent on who you are, I guess. Just be glad the entire industry isn't so good at protecting their content.