Ease of adjusting commercial midi files or old songs that I have is one of the strong points of my G-70: using the MakeUp tools it's very fast to browse the original sounds of the song and change them into the new sounds available, and to adjust some small things like levels, effects, panning, etc.

I can understand that recording MP3s is an easy way for porting existing material, but in this case you cannot profit of the new sounds and features available in your new instrument, and I think that it's just for these new opportunities that we change our old keyboard with a new one.