We started well with preorder but it hasn't worked reliably at all. We set limits for the number of products that were allowed to be preordered, and it has allowed many more to be sold. This has caused us big problems. Basically the app has failed to control stock properly.
Had a free plan and then changed it. I don't trust apps that change their pricing and force you to update to adapt to it. Bait and switch.
Thanks for your feedback. We have forever free plan which allows you to enable pre order for 1 product.