The tech press has called it "boring," as despite its new 4-inch screen the iPhone 5's improvements are mostly incremental; it's thinner, lighter, and faster. The two million people who've preordered the iPhone 5 don't seem bored by it, though. And even if the iPhone 5 were a bore, that's hardly a major weakness. (A smartphone that only lets you place calls if you amputate your finger, like with the iPhone 4's "Antennagate" -- now that's exciting.)
It's too early to tell if there will be another Antennagate incident with the iPhone 5, simply because it's not gotten into many people's hands yet. And part of the reason Antennagate drew so much attention from the tech press in 2010 is because it was unheard of, as was Apple's response (the company gave away free accessories that fixed the problem for affected users). For all of its power and features, though, we already know that the iPhone 5 has a handful of weaknesses ... one for each non-amputated finger.
Your apps aren't likely to just stop working on the iPhone 5, since it probably runs the same version of iOS that your existing iPhone does (if you have one). Most apps aren't designed for its taller, 4-inch screen, though, which will cause a letterboxing or pillarboxing effect when you try to use them, like the black bars that you see across some widescreen movies. App developers are scrambling to update their apps, but expect to be reminded of your early adopter status for a few weeks at least, to account for App Store review times.
Long-time Apple fans are used to needing to buy a new case for each device generation already (especially if they're fans of the iPod Nano), so this one is nothing surprising. Just keep in mind that your custom faceplate or skin-tight case won't work on the iPhone 5, and the specific one that you want may not be available yet.
The iPhone 5 dropped the old 30-pin connector that previous iPhones and iPods had, in favor of Apple's slim new Lightning port. This may be a problem if you've invested in an iPod dock, like for a home stereo system, as Wired's Roberto Baldwin reports. iFixit's Kyle Wiens believes that "the most expensive accessories will be the ones that won't work," and it doesn't help that Apple's Lightning Adapter doesn't have "iPod-out" support.
No simultaneous voice and data
That is, on Sprint and Verizon's networks the iPhone 5 can't browse the web or use web-enabled apps while you're making a voice call. Brian Chen of the New York Times has the technical details for why.
Trouble using your iPhone 5 internationally
Decided to go AT&T because of that last one? Your AT&T iPhone 5 won't have a 4G LTE connection outside of Canada and the United States. That's according to "professional amateur" Duncan Davidson, who wrote up a long summary of the pros, cons and costs of using each network's iPhone 5 abroad.
This last problem isn't really specific to the iPhone 5, and none of them are necessarily show-stoppers for any particular person (they certainly aren't killing the iPhone's success). They're still worth keeping in mind, though, if only to factor in the added cost of getting a new iPhone case and adapter.
Jared Spurbeck is an open-source software enthusiast, who uses an Android phone and an Ubuntu laptop PC. He has been writing about technology and electronics since 2008.