That disclaimer in the manual has nothing to do with the vocal harmony parts. These same presets work correctly in the PSR8000, 9000, 9000 Pro and 740. It is reasonable to expect them to work in the 2000.
The fingering mode is not enough of a bug for me to change OS, since I use the same one all the time anyway. It is an intermittant problem that is there sometimes.
If what was listed is all that 1.20 changes, I would wait for the next one.
Just be sure you are on record with Yamaha as having problems BEFORE the warranty period is up.
DonM