The only problem changing from one registration to another with different sounds (in the left or right part of the keyboard) is that the effect processor resets to the new sounds. This has the unpleasant consequence to cut abruptly the sounds from the first registration; this annoying effect is shared also by other Yamaha keyboards (like the Motif), while Roland (G-70 and also Motif) seem to be immune.
For this reason, if a Reg. has a sound that tends to linger (like a synth pad) I try to avoid playing new notes just before switching from one Reg. to the next.