Zach Schneirov, who maintains the wonderfully minimal Notational Velocity notes app for Mac OS X, has added full support for Simplenote syncing. You can get Notational Velocity for free or read about how his implementation handles various syncing scenarios to provide a very robust experience.
A lot of people have been anticipating this since we announced it a couple months ago, but we think this layer of extra polish has been worth the wait!
Since Notational Velocity also supports seamlessly storing notes as text files in the directory of your choice, you can also use it with Dropbox to synchronize your notes across a variety of systems. Just point Notational Velocity towards a Dropbox directory and you’re all set.
Simplenote 
Thanks! This is awesome.
The long awaited day is here! Hooray! Thank you!
I’m really enjoying Notational Velocity. Wouldn’t have used it if it weren’t for Simplenote, that would’ve been a shame. Is there an application, maybe outside of Textedit, that opens up so fast?
wonderful!!! the combination simplenote iphone-simplenote cloud-NV is a great note keeping system. well done!
I’m very interested in this service, but I can’t figure out what SimpleNote costs.You need to make your pricing scheme FAR more transparent. At the moment you’re destroying your reputation.
Me again. I finally found your premium link.Your pricing sounds more than fair for me, but you need to make it much more clear where your revenue is coming from. When I see a "free" app I figure there’s a con somewhere. If I see that there’s a way for the vendor to make money I feel a lot better.I fully expect to sign up for your premium service when my 1-2 week personal testing is done.
@John: Thanks for your feedback about pricing transparency. You’re right, it’s not clear enough right now what your options are for using Simplenote. We’ll work to improve this as we continue to refine the site.
What is the chance there will be synchronization with a PC-based client? In keeping with SimpleNotes approach, I don’t think it should be anything heavyweight like EverNote. I’d even be happy with some simple tagging that could be used with NotePad++.Using a text format would require users to be careful not to break tags when editing locally. Also, this leaves the sync to be done by something else. That something else could be Dropbox if the SimpleNote servers could sync to the user’s Dropbox (something like what you do with Notational Velocity).Of course, I’d be happy with something a bit more elegant if that were in the cards.Any news on this would be very helpful.