It's always a good idea to have a full backup of your setup. If you haven't done it before, now is of course a good time.
As far as I can tell, the samples (pianos and synth samples) stay as they are, but since the programs are now referenced by name from songs, and synth presets likewise from programs, it means your programs and songs have to be converted when the update boots up first time (looks like the format/version number changes, IIRC). If you have multiple programs/synth presents with the same name, they will be renamed (like in "my program" and "my program" would become "my program" and "my program 2").
If this process for mysterious reasons would fail, then your songs/programs/presets could be at risk, and you cannot just flash back to a previous OS since the song/program/preset structure likely changes and the old OS probably cannot read the new structure (didn't test this, though).
So... if you are cautious, make a full backup and you can then restore all, if the update fails to convert all your programs correctly.
If you are just a bit worried and know what you are doing, then you could consider backing up your presets, programs and songs only (as described above).
If you don't care, you could just go ahead and upgrade. There is a good chance it works -- but of course you could have some combination on your particular board that hasn't been tested because no one else made the genius setup you have
You can use the old song manager for the backup, but after you have upgraded, you need to use 7.10.
I didn't have any problems here updating/converting my setup. But I did make a full backup of all, and it took some hours to do.
It's a good update; the tweaks to e.g. unison are nice (I think) and also the changed analog delay is more musical ("instant headhunters" I guess)
And the new displays and list views are easier to navigate. The bug fixes are also much welcome, and the FM stuff is also improved.