I started practicing Zettelkasten recently, using The Archive[1].
I already had a pretty large collection of less-structured notes from nvALT, and I love how the new "rules" really help to shape my new notes. I'm converting old notes as I have the time and need.
I was initially skeptical of the idea of timestamping notes in the filename, but I find it counterintuitively useful, and The Archive has really good support for it w/ the Cmd-U shortcut. The Archive also has multiple tabs, which help immensely over nvALT's single pane.