My wife and I are both upgrading from IP4. I could list lots of reasons but it really comes down to two: 1) we are invested in the apple ecosystem from computers and tablets to TV and 2) we appreciate the integrated and highly functional design over slapped together spec beasts.
There was never a question that my wife was going to get the IP5. I however really wanted to have a hard decision in picking my next smart phone. I wanted to be tempted by android, tantalized by WP8, or spec excited by something. But it was sadly a no-brainer decision. I need a no-nonsense smart phone that keeps the mobile in mobile, and I love how everything works and appreciate the how tightly all of my devices connect together. Game over. IP5 for the win. It was't even a competition.