It really is great, I've been using it for years -- and all my notes are stored as plain-text (markdown) files. Only downside is images really. If you want to try it, check out this more-recently-updated fork. The creator of the fork is apparently working on a replacement that I'm rather looking forward to trying.
nvNotes[1] was great, but the latest version removed Dropbox syncing (because the developer was using an older API that is being deprecated) and now it's... no so useful. Combined with nvALT[2] on the Mac, this used to be a great combo.
http://brettterpstra.com/projects/nvalt/