I started playing around with a Lumia 530 on T-Mobile which has HD Voice and the call quality is night and day compared to my Nexus 4. Everyone I've talked to says the calls sound dramatically better and I'm not aware of anyone who has HD Voice capable phones. The noise cancelling seems to be a big thing as most people tell me that they can't tell I'm driving when I have them on speaker phone.

I didn't realize it had HD Voice and chalked it up to Nokia just knowing how to make a decent handset.