I agree. I spent quite a few years working in Digital Preservation, and what we found is that as evil as you paint them, a big corporation with lots of money will outlast an individual with pure motivations. That's why we can still read DOC files today.
Speaking realistically, investing your personal data in this project is currently a much greater risk than using Evernote.
The app doesn't work without an active web connection -- it's just an empty shell. So if the website goes down, I've still lost my data unless I back it up in advance.
Speaking realistically, investing your personal data in this project is currently a much greater risk than using Evernote.