I can see tons of arguments for going premium, too. Going paperless would push you over 60MB in a heartbeat. People who travel might want offline access. You can also get note versioning. This one's actually cool: they provide PDF search, which is sweet because most PDF searching and organization apps suck (please don't mention Papers).
[Note: I am not an Evernote employee. Just someone who's used it since 2009 for everything.]
Mind if I ask why not? I'm a big fan, though I admit it's a bit niche. It only works well for academic papers, really.
For more general PDF organisation, have you tried Yep? It's been a few years since I've used it, but seemed to work well.
Links: http://www.mekentosj.com/papers/ http://www.ironicsoftware.com/yep/
That said, I did pay for it for the year hoping that it would encourage me to use it (better organizing my work-life seems like a problem worth solving) - it just didn't...
But what really got me using evernote is the combination of Fuji Scansnap + Evernote. Now any important mail or receipts I need archived I just scan them and they're in evernote forever.
And their iPhone app is a life saver, anything I need on the go, I retrieve from evernote. Forgot my health card? No worries it's scanned and available on my phone via evernote.
I love the product, but yeah it still boggles me why they need so much money and how you can build a big company from such an inexpensive product.
Their 60mb/mo free offering is much more capacity than I actually use though, so I've never needed to upgrade. But I totally would if my needs increased or if they had to lower their free tier allowance to stay viable.
Evernote already has a large number of paying users who trust them enough to keep this type of notes with them using things like evernote hello, evernote food, etc.
http://www.metafilter.com/contribute/search.mefi?q=evernote&...
On another note the app seems to get heavier and heavier each update, it takes as long to launch as MS Word on my Mac.