How do I get my apps from device A to automatically install on device B when I sign in to my Google account? I have heard that it is possible for apps to be automatically synced between Android devices so that when you sign in to another Android device with your Google account, your applications will automatically be redownloaded for you without you having to manually do so.

I have a Nexus S which I do reset often, but it has never redownloaded my applications when I sign in to my Google account. I have checked the box 'Backup data to Google servers' in the settings.

So how can I get my apps to be automatically downloaded when I sign in with my Google account?
If you go Menu -> Settings -> Privacy there are two options.  They are Back up my data and Auto restore.  Are they both checked?