What do I need to backup through Titanium for a smooth recovery?

[Guest BillBong]

If I want to move from one ROM to another, will it screw things up to do a complete system/apps+data backup and recovery? The problem seems to be when some ROMS have different versions of the system components (like the google apps/talk/maps etc) so I'm not sure what settings I need to use.

I basically want to just be able to restore apps+settings without messing about after flashing a new ROM but I'm not sure if some of the system things that are backed up are ROM specific