I decided to try this out, as it allows you to make notes or import and have documents available on the iPhone for use on it later when you're away from your main computer. It certainly does that, as I found out when I moved a bunch of PDFs about an upcoming trip to it. Move a PDF to the Evernote window and it imports and then click it and drag to one of the tags you want to apply, and it applies it to the item.
But even better, I was driving on the highway to a hearing today and heard something on the radio I wanted to remember. I couldn't stop to write it down, so picked up the iPhone and went to Evernote [with a minimal amount of hassle] and pushed Voice Note and dictated a memo to myself to check on later. Worked just great. It wasn't anything particularly long, just a snippet, but it was easy to save and now I have it for use, later. I'm sure it does much more, but this is enough to justify it's 'cost' [free at the iTunes App Store].