There are services that provide richer functionality than Simplenote, but the very appeal of the service implementation is that it keeps things simple. A such it's ideal for quick reminder type text notes - the ones you use to write on post-it notes. There is support for tagging and searching, plus the ability to share with others, but those features are entirely optional.
The Metro Note app doesn't require you to sync with Simplenote - it can operate in standalone mode - though you will need to click through the log-in screen every time you open the app. However, given the extra flexibility of cloud sync, the ability to turn off automatic sync in options and the fact the basic Simplenote service is free there's really no reason not to sync.
When you open the app you're notes are shown in a list format, with the title (first line of the note), timing and tag information displayed. Buttons on the toolbar let you add a new note, sync notes or search for text string within your notes. Tapping on a title opens the full note, where you can edit, apply tags and pin it (stick to the top of the notes list).
Marketplace description:
Metro Note syncs your notes to the cloud using a free service called Simplenote, allowing you to easily share notes across your Mac, Android, Windows, Linux, and other devices. Good for keeping your grocery list, remembering what to buy at the hardware store, and minimizing those important scraps of paper that always seem to get lost.
Metro Note, which has been developed by jtl, can be downloaded from the Windows Phone Marketplace. A free trial is available, with the full app costing £2.29/ $2.99 / €2.99.