I haven't found a solution that can replace this on OSX.
Using the software that came with my ScanSnap I just push the button on the scanner, and an OCR'd PDF gets added to my folder of scans. I could then just add a symlink to this from my Dropbox folder and have them immediately synced everywhere.
That also made me sad when Simplenote was bought by Automattic and became free as consequence. It was great that Simplenote was not simply shut down, however, 'free' is not a business model I want to rely on. But Simplenote is still the best although it has some reliability issues too.
As a general side note, syncing – even of relatively simple text notes – is a challenge. If you really on synced data, there is no way around having your own independent local backup with some kind of versioning.
For editing: Sublime Text on my netbooks/macbooks. Editorial on the iPad. WriteRoom on the iPhone.
Works for me ;-)
Evernote is too expensive, too slow, and too clumsy for my simple use-case. I use the free version, but again - too slow, too clumsy.
It's a lot like Notational Velocity, but for Emacs. I've used it for over a year and love it.
I just use it for text notes though. Evernote works great for me - I'm not going to worry about it.
Seriously, at this point we've covered every facet of every note taking or todo app. Enough already.