The sound quality is fine; they don't seem any better/worse than the standard issue Apple earbuds to me.
The noise isolation is great for loud environments. I listen to podcasts on the NYC subway. With earbuds I had to pause it every time a train was arriving/departing (loudest volume wasn't loud enough); with these I can keep on listening.
The noise isolation makes it weird to talk on the phone (or to other people in general). You can't hear your own voice. Maybe you could get used to it, but it's easier for me to pop out one of the ear pieces.
Keep the set of rubber pieces around for a few days, to be absolutely sure you have the right size for each ear.