I use NotesNook. Just imported from SimpleNote a month ago without issue. If you are like 95% of people and take very few notes, consider using Simplenote since it starts up fast (including on mobile), syncs across place is very quickly, and gets out of your way.
NotesNook is very similar, but has some additional features for organization and rich media. After using Simplenote for over 5 years my notes are starting to need some more organization.