The lack of notification options is my biggest pet peeve with the iPhone. For all its amazing features, it is still way behind in basic cellphone functionality, like providing repeated notifications for a missed call/text, not just the single beep/buzz. The iPhone has a sophisticated setting system, just give us options for notifications. People like me who want a beep/buzz every couple minutes until the message is picked up can have it, and people who don't mind not knowing about missed calls/texts can have it their way.
On the same subject, the actual power of the vibration needs to be increased. I can barely feel the vibration when my phone is in my pocket. I used to be able to feel my old Motorola no matter how noisy the environment, so I rarely missed any calls. I'm missing a huge number of calls now 'cause I just don't notice my iPhone going off.