Notational Velocity as notes app
Notational Velocity is an excellent 'cruft free' note taking app. It doesn't hurt that it's Free Software either.
To keep the formatting for your notes the same accross all installs of NV you will need to turn on 'soft tabs' (converts tabs to spaces) as well as setting a 'fixed width' font.
This is due to Simplenote defaulting to stripping out tab's in favour of soft tabs.