I have been a loyal Evernote premium payer since 2009, and using it even longer. For a long time I recommended it to friends but since have stopped. I have developed some concerns with it over the years. 1. Fear of data loss... it's probably the largest part of my mistrust of all these dang cloud services that want to control/own me or otherwise lock me into their service. I run a 99.999% uptime, extreme scale, SaaS…
Anyways, I enjoyed your comments wanted to give my personal opinion & point of view for at least points 1 & 2.
1. You're right that scaling is very hard. If you want a closer look at it, we have a tech blog that even I can read and understand. https://blog.evernote.com/tech/ Perhaps the most reassuring thing I can say is that Evernote runs on Evernote. Err... maybe this is more clear, Evernote (the company) runs on Evernote (the service). We eat our own dog food as they say, which means I've lost count of how many water cooler conversations turn into "there's something weird that Evernote's doing on my computer..."
2. Our Mac and Windows apps let you export your notes into HTML (including resources). Both these apps run natively against local files so you could export if you were offline or if for some reason our service was down. We try to compete by making a great app and a great service. In fact, we don't make money unless we've done a good enough job for you to upgrade to Premium. It seems like your main concern is that your text-only notes export to HTML instead of plaintext, which is a fair point. One of the nice things HTML is that there are third party applications that can convert from HTML into a number of other formats, so we're relying on that if you want your notes in RTF or as a .txt or something else.