I have a 27" Quad Core iMac, 13" MacBook Air, iPad and iPhone 4. I love them all. The moment some other company brings out a similar range of devices that work together as seamlessly as these do and I will jump ship seeing as I hate Apple intensely.
I am yet to experience an Android based device that rivals the iPhone for how I use it when it comes to phones. Having said this, Gervase may have one that could rival it based on his description.
As for music players, I cannot comment from experience as I will never carry a music device around with me as well as a mobile phone which again makes the iphone a great solution. Add TomTom as yet another feature of the iPhone and I find it hard to beat. The days or removing the sat nav from the windscreen and hiding it somewhere in the car is gone.