Yeah... I do pull in some system-level bits.... Wifi hotspots, SMS messages, call logs... I've had luck bringing in the Google App data (which allows me to maintain my launcher settings). But I don't go much beyond those. But I am flashing new versions of custom ROMs all the time, so I've come to see exactly what data is needed to maintain my preferred config, and what data is just chaff and there's no need to back up.
I wish there was a setting to set aside some apps to only back up the app and not any app data... say for games and apps that use cloud storage for config (Google apps, games that use GP Games, etc). TB has settings for external data. I gotta go look up exactly what that entails.