I was thinking of buying the nexus too but finally I decided to stay with my iPhone 4 jailbroken. Ive added cool stuff like new widgets to notification bar and 4 different ways to access the multitasking bar and a one tap solution to end all open apps. Now its waaaaay more easy to multitask.
For maps I use TomTom, which is great.
Google Navigation requires you to be on 3G. iPhone GPS apps like Navigon or TomTom don't require 3G because they have maps downloaded. Its way better. I could never use Google Navigation or Apple Maps if they require 3G because 3G is NOT available on every area where I live. Its just pointless then. TomTom or Navigon is the way to go. Yes, they are not cheap, but thats not that big of a impediment.
Elsewhere, Android sucks at games. No Sonic, Assassins Creed (the android version is 2D, sucks), Monkey Island, Rayman, Super Monkey Ball, Dead Space, Modern Combat 3 (this game is just impressive), Street Fighter, etc. The BIG games are on iOS. Why? Because it requires developers to develop these games for just one or two devices: iPhone 4 and 4S (and maybe 3GS).
Also, copying my music from iTunes to Android seems difficult. Before I didn't like iTunes, but now... man, its the best program in the world. One program to store all your apps for iPhone, iPod and iPad, your backups with just one click, seamless syncing, books, tv shows, movies, music, podcasts, updates, etc.
Ive had many phones before the iPhone: Nokia, Samsung, etc. I hated having to flash new ROMS to the Samsung to get updates. I know how to do all that stuff but as I grew older I just don't want to keep doing that stuff. I want something easy to use, since Im not gonna spend many hours of my free time searching the web for ROMS and ways to install them. Not anymore, it was exhausting.
I wish iOS had some stuff from Android, of course. I like Android, just not enough to change OS. Thanks to Android we now have a cool notification system


I will stay with iOS for a while and wait for Apple to bring new stuff on iOS 6 and 7 and later.
I even wanted a bigger screen than iPhones 3.5, but after watching some videos from the Nexus and other Android phones I just understood that they are indeed very big phones. For big screen I already have my iPad. I think a 4 screen would be good, but the 4.65 of the nexus makes the phone too big for my taste. But I do like A LOT the buttons on the screen. I wish Apple did this.
At the end of the day, I prefer an easy way to backup and sync (iTunes) than bigger screens and other stuff from Android. Im sure next year or in the following iPhone will get bigger screen and other necessary stuff.