I recently got an S4 after being an avid Apple user for the last 3-4 years.
The flexibility associated with Android is refreshing and especially for someone like me who likes to theme my device.
What's completely undoable on an iPhone without jailbreak is par for the course on Android. Stuff like custom icon packs and fonts, custom launchers where you can influence how folders look, icon size, dock setups, animations etc etc etc It's prolific and we not even talking about the benefits of rooting and the weird and wonderful world of custom roms!!
The quality of apps on Android platform is quite surprising too. Splashtop, Teamviewer, Dropbox, Skype, Twitter and Facebook are apps I've used extensively on both platforms and I prefer them on Android. Size of the screens has a lot to do with it though but there's absolutely no problem with the quality of how the apps have been written for Android...
What I will say is there is a smoothness in the Apple UI which 4.2.2 hasn't quite replicated. Bloody close but not there yet. I understand a custom rom is a different animal in this regard. Will flash and revert...
iOS 7 is a massive step in the right direction but if Apple really want to close the gap they need to endorse the jailbreak and the jailbreak community and start appreciating what they bring to the table and to iOS...