Quote from caementarius:
After you have the installed software you need installed, you bundle a new instance that is yours alone.
You can save data without bundling an instance (which seems to take like 20-30 minutes or so(. To do this you create a volume and attach it to your instance. Also, you can lease a static IP and map it to a hostname (using your own DNS services). This makes it nice so you can remote desktop to the same hostname.