First and foremost Q: do you need a smartphone? (I'm assuming that you don't already have an iPhone, as you didn't say so.)
Yes, seriously -- do you really need/want one? Would you use any apps/games? Would you watch videos? If not, the iPhone is probably not for you. Note that the iPhone is fairly expensive (not the phone, but the monthly service charges with the 2-year contract).
If the answer is, "yes". Then the iPhone may be a good phone for you, as you as you understand and accept the following:
- The iPhone battery life sucks. The life is somewhat dependent upon your cell signal strength, and what features are enabled (I enable everything), but it's not unusual to get a day (or less!) of useful battery life. Also, note that the iPhone's battery may seem to be especially bad for the first few days; you should calibrate the battery meter (once) by charging to 100% and using it until it dies (in normal usage, you should only do this once a month or so, as doing this too often will hurt the battery's overall lifespan).
(Yes, yes, for those people who feel that they must take exception to this, this topic has been shot, dug up, and shot again: https://forums.macrumors.com/showthread.php?p=7961354#post7961354 )
- Carrier coverage may be an issue. With AT&T, some people have great coverage/service; others, not so much. It all depends on where you live, work, and travel. Note that some major metropolitan areas may appear to have good signal, but suffer from congestion (dropped calls, slow 3G, etc.)
I love my iPhone, but I also realize that it has shortcomings.