Three main things (and a few minor ones) are keeping me on iOS, despite the fact I also own a Samsung Galaxy S3 (rooted, SmoothROM Jelly Bean 4.2 RC2).
1) one of my cars has an iPod/iPhone 30-pin connector (works with the 30-pin to Lightning adapter for my iPhone 5) but does NOT have an aux. 3.5mm audio input, so I can't use it with anything else but an Apple device.
2) wife and kids use iPhones, too, and the Find My Friends app comes in so, so handy.
3) this one is most serious and has no good work-around presently. My workplace uses iPhones has the preferred device for connecting to the work email system. iOS devices are permitted to access the Outlook servers natively, giving full access to documents attached to email, iOS access to the Outlook calendar, etc. On Android and Windows Mobile, you are required to use and app called Good for Enterprise. Native access to the Outlook server via the native email app is not permitted. This POS is so locked down that I can do nothing with attached files but view them using the app's crappy built-in viewer. If I want to save/edit, I have to forward them to another email address outside the work system - the app (presumably set by our IT) forbids saving attachments or opening them in any another app. And we're also forbidden to attach documents from other apps on Android/Windows via the Good app. On iOS, I can attach any document from any app that allows me to do so (GoodReader, Adobe CreatePDF, iWork suite, etc.). This is completely restricted on Android/Win Mobile thanks to the Good app. Similarly, calendar access is trapped within Good, but fully accessible via the iOS native calendar.
I could probably work around #1 and 2 (and the other minor ones) above, but #3 is the deal breaker. It makes it nearly impossible to get any substantial work done on-the-go with the restrictions imposed on Android and WinMobile. And as far as I know, there are no plans to open native client access on Android or Win Mobile (and actually the Good for Enterprise app doesn't work on Win Mobile 8, only 7.x).
Yes, the IT department as work is very, very restrictive in terms of security on the work network.