30% of them think that Evernote loads too slow.
26% use just few of its features.
13% feel that it's too expensive.
Some of them need better support for specific tasks they use Evernote for: storing code snippets, embed images, use notes offline, hide some of the notes, draw sketches, etc.How do we know? This is what people answer on the survey.
I use Apple Notes occasionally, while don't like others yet, because of my fears: Google Keep is a side project for Google, they can drop it at any time, like they did with Google+, Google Reader and many others.
Microsoft OneNote seems to be too rich with features. Also, it looks good on a large Microsoft Surface, but seems to have overloaded user interface on a tiny iPhone SE.
How do we know? This is what people answer on the survey.