I too throw everything into nvALT these days. I love it. The main differences between my workflow and Dave's are that I don't use Simplenote for syncing—I use Dropbox (why rope into my setup yet another third-party service?)—and I use Notesy on my iOS devices. (If there's a better Dropbox-aware note-taking app for iOS, then I haven't come across it.)
Relatedly, nvALT is merging with its progenitor, Notational Velocity (apologies--I can't find a link for this bit of news, but I'm certain I read it somewhere), and Brett Terpstra tells me that eventually we'll be able to post to WordPress blogs directly from the app. Woot!
Another neat thing about nvALT is that it has an "External Text Editor" option that lets me jump seamlessly between it and Writer, despite Writer not (yet) supporting the ODB Editor protocol and thus being unable to take advantage of QuickCursor.