Also, I believe phone calls end simply by closing the phone application.

I accidentally launched a phone call once and it suddenly dawned on me how awkward it is not having an end call button. I panicked trying to cancel and multi-tasked away from the phone applet. I quickly hit x next to the phone application and that was the end of that.

Was glad its that simple but also would be easy to accidentally end a call if multi-tasking at the same time, but then that's always a risk with multi-tasking, closing the wrong thing.