Too right it retains a resale value.
Bought the 4S when it came out, sold it six month later (to foolishy try out the Galaxy Note, horrible bit of kit) for the exact same price I originally paid, less eBay fees.
I'm really gonna upset a few people here but the iphone has always been nice hardware but the software was designed for those who couldn't set the timer on their vcr (when we had vcrs).
iOS that drives the iphone and ipad, does have have a very polished feel to it and given apples ability to do that for the last 24 years its no surprise.
But its marketed as a smartphone and tbh it really isn't a fashion/semi smartphonish is a pretty good description. if you want a bit designer bling which says "smartphone" then sure its the right device for you. Same with those who want zero customisation and "it just works" attitude.
That sadly is most people.
The worrying thing for tablets is this, just like how intel killed the netbook, apple will kill the tablet arena (along with android) because of the limited nature of the apps that are on the ios platform (partly due to the limited nature of the os).
Microsoft well just lets say win8 looks like a dogs dinner ..