I've made that switch recently, after losing some stuff in Evernote for what I decided was the last time. I briefly messed around with SimpleNote, which was immediately doing weird stuff with tags (duplicating, not accepting changes). Then, I replicated my Evernote structure with folders and txt files in Dropbox. It works perfectly. And, there's a bunch of clients that edit txt files right in Dropbox, like Byword (OS X and iOS), Plaintext (iOS), Notesy (iOS), Ulysses (OS X), TextEdit + Spotlight (OS X), etc. You can switch apps on a whim and leave your data in place, and the syncing has been great. Simple, clean, and non-proprietary. I haven't checked into audio recording + Dropbox, but surely there are mobile apps for that, too.
Totally. I've got an encrypted sparsedisk image for anything that needs to be truly secure. That's definitely a caveat though, because its contents can only be edited from my Mac. On the other hand, I didn't trust Evernote that much either.
