At the risk of going too far off-topic, let me sound a note of caution on nvALT (and other similar applications that work with Simplenote): when you have a large number of notes, the combined search/create interface causes problems (though this may not be true with the latest Macs with lots of RAM and an SSD). It often happens that I start typing a title with the intention of creating a new note, but nvALT starts searching through all my notes as soon as I've typed a couple of characters, preventing the other characters I've typed from being input properly. If I start retyping them, though, nvALT will sometimes partially catch up to my previous input, leading to an unpredictable number of duplicated characters in the note's title. Although John Gruber and many others sing the praises of the app, I think the decision to combine Creation and Search was a bad one. For comparison, you may want to recall the early days of Spotlight or searching in iPhoto or Mail.
In addition, I've found the sync to be unreliable, regularly deleting portions of my notes when I sync between Simplenote on my iPad and nvALT on my Mac. The developer is very sympathetic, but there doesn't seem to be any way for him to investigate individual cases. To be fair to Simplenote, it doesn't sound as if these problems are very common, but they're also not exactly unknown: Merlin Mann has occasionally mentioned loss of data in his podcasts, and Michael Schechter wrote in May about a similar issue: