Recs.
Updated
A cross platform note taking app with built in cloud synchronization. Minimal in appearance, this is an app meant for taking notes as simply as possible.
Read PC Magazine review.
SpecsUpdate
Pros
Pro Geared towards fast usage
Unlike alternatives (such as Evernote) that are laden with features, Simplenote is fast to use and sync. Reviews from the Verge, Lifehacker, and a variety of other sources all describe using the Simplenote apps as very fast. While it may not be as feature-rich as other apps, the responsiveness of the app and simple interface keep it easy to use while never slowing down the user when they need to quickly take a note.
Pro Very simple and clean interface
Simplenote takes a minimalist approach to its interface. There are no toolbars full of formatting options or extra features like notebooks to group notes. The entire desktop interface consists solely of a sidebar with your tags and trash filters, the list of existing notes with search, a button to add a new note and a simple view for looking an existing note or writing a new one.