Rather than a simple address book for contacts, Windows Phone uses the unique People app to bring all of your networks to one place. This includes your standard phone contacts from a SIM card, email lists through Windows Live, Google, and Outlook, as well as your social networks including Facebook, Twitter, and LinkedIn.
Drawing contacts from so many places can become overwhelming, but thankfully there are useful filters by network and the option to create groups for better organization.
In addition to the complication of having too many contacts, pulling lists from multiple social networks often results in individual contacts having multiple profiles. These too can be managed with a chain icon that allows you to link contacts together into a single profile page. Sorting through the long list of Facebook and email contacts can be a tedious process when initially setting up the People app, but the resulting compiled contact list is a beautiful thing to behold.
Since the People app ties into your social networks, it also provides a compiled news feed of Facebook, Twitter, and LinkedIn updates. The social feed can become overcrowded quickly though, so most users will be much happier opting to download dedicated apps for each network.
Call quality was excellent overall, though the phone's default settings were a bit soft and required a slight volume adjustment. Switching to speaker phone provided similar results, with excellent quality after raising the volume.