HD voice calls on the iPhone 5

I have just had my first iPhone 5 to iPhone 5 voice call with my brother. We're both on T-Mobile UK, which runs on the newly formed EE network with support for HD voice calls.

The sound quality was amazing. Initially i was taken-aback and thought I must have switch on the loud speaker. A quick glance at my phone's screen showed that I hadn't. The crispness of the sound is startling when compared to the audio quality of phone calls I ever have before. It was like someone whispering into your ear but talking at regular volume.

Now I'm not a heavy voice caller, but I have to say HD voice needs to be heard to be believed.