I’ve just discovered Demiplane and it seems like it has potential.
Quick question that will determine whether it is actually useful:
Can I use my own PDF contents, or is this yet another platform for which I will be required to re-purchase all of my content that I want to use?
Bit of a long answer, since it differs by NEXUS:
If you own a PDF from the Paizo store, you can use your Paizo Connect account to get a significant discount on each title you purchase here on Pathfinder NEXUS. Similarly, when Vampire NEXUS launched, Renegade sent out a discount code for anyone who had purchased physical Vampire books from them to gain access to the digital versions here. I believe that code is now expired, but we do everything we can to get great games into your hands at an affordable rate.
We’ll have more deals like that too. For example, right now if you sign up for a Demiplane Membership ($4.99/month) you’ll get three $5 coupons that you can use across three transactions to help fill out your library. And then if you purchase the Ultimate Bundle, you’ll save 25% on every title we offer in that NEXUS (this stacks with the Paizo Connect discount). Additionally, since we have content sharing, you and your game group can split costs and then share content with one another so you don’t each have to purchase everything. You can share with up to 24 other people!
I use Demiplane in my own games for easy reference of game rules, and think it’s worth the investment. But especially once we release character management for each game, it’s going to be invaluable for new and experienced players alike! 
Thank you for your informative response.
So what I’m seeing here is that essentially I have to buy everything again.
Sorry, it seems like a great tool, but having to re-purchase everything that I plan on using is a deal-breaker. I’ve already purchased most of my library at least twice…original PDF, Fantasy Grounds, and a couple of titles on D&D Beyond before I figured out I was buying everything again.
Ain’'t gonna happen.
I’ll check back occasionally to see if I can share the PDFs I already own. Until then I will sadly have to refrain from using Demiplane.