The ability to select what apps will be opened when you're doing searches, SMS, or even dialing from another application. If you hit Text Messaging, it will open up whatever SMS client you choose (instead of the default SMS client); dialing can select whichever VOIP client you want; "Safari"/links/ can open whatever web browser you want; etc. Some more interesting developments would be the ability to open up apps on the iPhone that would normally open up Safari (like say links pointing to Yelp, or Google Voicemails could open up GV Mobile +, etc.).