Review: HTC Sensation 4G
There don't appear to be any changes to the behavior of the Sense phone call and contacts applications.
By default, the phone app opens with the dial pad on the bottom half of the screen and your top favorites above it. The phone app automatically sorts through your contacts as you type a number/name, so you can sift through a large contact database quickly.
If you've synced with a Facebook account, the device automatically adds not only your friends' Facebook profile pictures to their contact info, it also ports over any phone numbers stored in their Facebook profile. It will easily handle thousands of contacts imported from Google, Exchange, Yahoo, etc.
The synergy between the calling and contacts apps is very well done with Sense. I like what HTC has done to make them one tool, rather than separate functions. For example, both the calling and contact applications share the same sliding tab at the bottom that lets you sort through contact groupings with a simple swipe of the thumb.
The Sensation 4G also has T-Mobile's Wi-Fi calling feature. It uses your home Wi-Fi network to make calls through the internet. It won't hand off to the cellular network if you leave your house, but it will help you keep some of your plan minutes saved up. Voice quality via Wi-Fi is fine. I didn't have any problems making calls using this feature and my home internet service.