Skype is also a service that lets you instant message people and place VOIP calls domestically and internationally. You could also use the back camera for your video chats
No front facing camera needed!
I can't believe some people's impatience. The Skype deal only closed recently, do you think Microsoft can get full Skype integration in that quickly? Most likely it will appear as a separate, last update for WP7.5 around May.