Hi
@Sewbee - I think I've covered some of this in your other thread but I'll answer again. I'm slightly different from you in that I do mainly P&Q with some garment sewing. I bought my 720 in July and haven't touched my 570 since then, so that definitely says something! I thought I would use both but it just hasn't happened.
The extra features on the 720 that I like best are:-
10" harp space (more for quilting)
auto thread cutter (more for garment sewing)
hover/pivot function (love this - specially for applique)
auto presser foot lift (couldn't live without this now, especially with my bad neck)
lower thread/bobbin empty indicator (great when you're quilting)
70% larger bobbin (as above)
better/more lights (my eyes are bad)
Don't get me wrong - the 570 is a gorgeous machine, and if I hadn't received the inheritance from my dad I'd have been really happy with it 'til the end of my days, but the 720 is like the 570 souped up. I was worried I wouldn't like the auto presser foot lift - there is no manual lever - now I've got used to it I absolutely love it.
Hope this helps.