I am just now coming back to Evernote because of it's ease of use. I love the simplicity of how documents get refreshed such as PDF documents when they are edited.
However, one of the reasons I left to use OneNote was that they have the ability to set up multiple levels of stacks. In addition, you could share them to other people. With Evernote, you can have one main "notebook" with stacks that contain notebooks. If you want to share the entire stack, you have to share it by sharing each individual notebook in the stack. I see all over the website about "time is money" and making efficiency the key to the use of Evernote. I don't see how this is working in this regard.
In OneNote, you can have multiple main "notebooks" that can be shared, you can have sub-folders with sub-folders that lead down to a specific notebook (I believe they allow up to 5 levels). At any rate, it would be nice to have something like this:
Anyway, it would be nice to "stack" notebooks in notebooks at multiple levels. For now, the ease of use out weighs the use of multiple stack levels, but it would be convenient to be able to have this feature in future updates.