Here I would like to discuss one of the HTC Sense functionality that mostly people doesn't realize. Since Sense 3, this function already embedded. This is how it works. In certain situation, when you are talking on the phone, and half way you want to talk using the loud speaker, normally people will find the loud speaker button.
But with HTC Sense, simply flip the phone and place on flat surface and it will change to loud speaker mode without finding or pressing the loud speaker button.
Now we are talking about the conveniences that HTC Sense offer to you.
HTC - The Smartphone that make Sense.