LOL- since you asked...
Best feature (which is what sold me on the software) is OCR. Otherwise, we would all still be using the notes feature of Exchange, since it is built into Outlook and syncs with the cloud as well.
But with Evernote, You can take a picture of a sign from your phone, then search text that appears in the sign later. I use this whenever there is a posted schedule (train times, zmanim for shul, etc), and I just snap a pic with my phone.
Then, from my office computer, I can type in a word that I know appears on the side, and Evernote will find all notes, pictures, etc, that have this word in them. PRICELESS!
No, it is not a resource hog at all, Asher. In fact, aside from syncing notes after you change something, it doesn't really do much in the background at all.