Youre in the middle of a game of Flight Control when the phone rings -- everything gets pushed out of the way and you must decide to "Accept", "Decline", or wait 20 seconds until its done ringing. Rarely, if ever do I actually "decline" a call -- most of the time I simply let it ring. Why? Because the caller knows that it should ring more than five seconds! They know that you declined their call!
I'd like to see an option to change "denying" a phone call to "ignoring" a phone call. Meaning that, should it be ignored, the phone will continue ringing silently in the background until it is sent to voicemail. This enables you to get back to your work and not have to waste the 20 seconds that go by. That also allows time for you to change your mind, should you decide to go back and take the call.
Other than that, multiple notifications on the lock screen that I can click on and go to the respective application: "1 new email from..." to Mail app. "1 new message from..." to SMS app. Etc, etc.