One thing I want to make clear, so no one gets the wrong impression. I'm a longtime, devoted Evernote user, and Evernote is a vital part of my working style. I typically use Evernote continually throughout my workdays.
Even though I don't like Version 10 much so far, it's still by far the best information-management tool that I've seen out there. I've looked at many of the others, and they just don't have functionality and flexibility/adaptability that Evernote has. That last part is particularly crucial. I'm sure that like many users, I'm utilizing Evernote for things that the designers may not have envisioned.
Aside from the tags/subtags problem, my big discontent with Version 10 is that they've ditched numerous features that were really useful. However, I'm hopeful that some of those features will be restored or improved, especially if there are more frequent releases going forward.