If you are going to be resetting your Android, or upgrading to a new model, default backup and restore options for the Play store and some applications can help the transition go smoothly.
Having had both an upgrade and a reset in the last month, I thought I'd document what didn't work for me.
This relates to Android 4.3, on Samsung Galaxy models (believe this process will span a few models and versions)
Play Store "restores"
If you backup your device though the settings menu, your app selection will be saved to your google account, and apps with be reinstalled on reset if you select the appropriate options at start.
However, the apps may not be the apps you had installed previously.
I found that a number of apps I had previously uninstalled were reinstalled. Also, a number I had installed weren't automatically installed, but were in the list of "my apps" .
To mitigate this: if you have the chance, before reset/upgrade, go to the Play Store > My Apps > All menu, and click the remove option ('x' icon) on any apps you know you have uninstalled. You can tell which these are because they will have this option (installed apps show as 'installed', and require uninstallation before removing). Also, any apps that make you go "ew, I installed that?"" upon seeing their application icon will also require removing.
You may need to install a third party app to backup these to file, then upload the backup to Dropbox (or similar). Upon reset, install the backup app and preform the restore from this backup file (on reset, the phone advised me that there was a Samsung way to do this, but I already had my backup, so I didn't investigate)
Third party backups
Some apps have a lot of data you want to keep. For example: ADW desktop layouts and settings, Swipe or SwiftKey predictions. You'll have to go through your own list to backup and restore these yourself. Any app that allows arbitrary backup and restore from file will be easy.
The apps that don't backup
Twice now I've lost my Noom pedometer step data, because there's no way I can find to back this up. The application requires that you log into an account, but doesn't store step information against your account, which sucks. Other Noom products do, and have export options, but not the Noom Walk app. You may encounter the same issue with your apps.
There should be an easier way to backup and restore or migrate devices, but since a reset is usually to fix/debug more serious faults with a phone, and upgrades have different hardware and core OS version differences, this isn't a one size fits all thing. Check for outlying apps before you blow things away to save yourself heartache.