I think the biggest improvements are the aluminum back and sapphire lens for the camera. No more scratched up backs means that people with case free iPhones can sleep a little easier. The bigger screen, improved battery life, and LTE (faster mobile Internet) were expected improvements. The new earpods earbuds seem neat and I will probably buy a pair to review them. The new lightning connector was also expected but means that you will have to buy all new accessories or a bunch of those little dock adapters. Many of the rest of the improvements are in iOS 6 so iPhone 4S users will be able to enjoy important things like enhanced Siri functionality. My recommendation is if you have a phone upgrade to buy the iPhone 5. Power users should obviously get the 32GB or 64GB models. If you already got the 4S and do not have an upgrade this year, then you will not miss a whole lot while waiting for the iPhone 5S/6 to arrive next year.
The new iPod nano is nifty. I’m not sure if I like the new form factor better than the old one. I think that I would take this as a good opportunity to snap up the last generation iPod nano at reduced prices if you are considering it.
The new iPod touch is also neat. Apple seems to be aggressively courting the point and shoot camera market and also the game console market. As an iPhone user I have little interest in carrying another device for my iPod. However if you have an Android or dumbphone and want to be able to use iOS apps then the new iPod touch is worth the buy.