It's clearly a better phone than the iPhone 4 - it has a faster processor, it has more RAM, it has a bigger screen, it's wireless data capabilities are faster, it's lighter and thinner, the camera is better - but having seen one in person, I can't say I'm that excited by it. I've got an iPhone 4S and as I find that fast enough and capable enough for everything I do, I see no need to upgrade. There's nothing with the iPhone 5 that demands my attention or need to upgrade. The screen isn't that much bigger, the wireless data transfer isn't that much faster. I'll hold on.
I used iOS 6 on my iPhone 4 during its development, and for all the disappointment as regards the mapping app, I thought it was brilliant. Worked perfectly well in my region (Sydney, NSW, Australia). I'm still not going to upgrade to the final release though. Not yet, anyway.
I'm a firm believer in "skipping a version" as far as Apple goes. The iPhone 5s(?) or iPhone 6 will be the one I go for, I suspect. Unless there's something else on the market more interesting.