Sprint is the only U.S. carrier to offer deep integration with Google Voice, allowing customers to use their existing GV number on a Sprint handset instead of just adding the Sprint number to a GV account (which can also be done).
We were looking forward to trying this out on the HTC EVO Design 4G, but sadly the phone number of our review unit wasn't eligible, throwing up an error when we tried to enable it from the Google Voice website. Regular GV calling worked just fine, however.
We also tested our favorite Google Voice-connected VoIP app, GrooVe IP, which places and receives free GV calls over your data connection (you'll need a monthly data plan, of course). In our area, Sprint's 3G service isn't exactly a speeding bullet, but it was perfectly functional for short (and free!) calls.
Otherwise, using the phone to make calls is pretty much the same as other HTC Sense-enabled handsets we've used. The dialer takes up half the display with five contacts displayed above, but the dialer can be tucked away with a tap. Smart dialing is also enabled here, so users can quickly start typing a phone number and see contact information filtered by name or number.
To the right of the green call button is Call History, essentially a shortcut to the People app, with quick access buttons for Contacts or Groups as well.
New accounts can be added under Settings > Accounts & Sync for the usual suspects: Google, Facebook (as well as Facebook for HTC Sense), Exchange ActiveSync, Twitter and more.
On the lock screen, users can quickly jump straight to the dialer by dragging the Phone icon down into the lock ring at the bottom of the screen. Android 2.3 Gingerbread still isn't our favorite when it comes to calls and contacts, but let's call it "serviceably adequate" and leave it at that.