What's their portability story? I don't want my personal knowledge store to be locked into a platform, particularly one that's not guaranteed to last. PDF exports don't cut it, my notes are living documents.
I'm really sad that nobody has adequately addressed interoperability in the digital inking space; I'd gladly switch to an iPad or reMarkable, but so far I'm still the neckbeard inking in Xournal on an old Thinkpad.