For me it's the apps.
Long story short bullet point style
* Irrational hatred towards Apple, had an Android phone
* Wished to buy tablet, better support for OS on Apple stuff than Android (had to resort upgradring to custom roms to upgrade Android phone as Motorola are useless)
* Purchased an Apple iPad due to higher quality apps IMHO
* Grew tired of Android apps being flaky in comparison
* Swapped the Android phone for an iPhone 4
* Result = happy with phone and not bothered nor tempted by the 4S or 5