As is typical with most devices that use rechargeable batteries. Mossberg didn't exactly pan the iPhone for its battery life:
"Battery life: Like the iPod, but unlike most cellphones, the iPhone lacks a removable battery. So you can’t carry a spare. But its battery life is excellent. In our tests, it got seven hours and 18 minutes of continuous talk time, while the Wi-Fi was on and email was constantly being fetched in the background. That’s close to Apple’s claim of a maximum of eight hours, and far exceeds the talk time claims of other smart phones, which usually top out at five and a half hours.
For continuous music playback, again with Wi-Fi on and email being fetched, we got over 22 hours, shy of Apple’s claim of up to 24 hours, but still huge. For video playback, under the same conditions, we got just under Apple’s claim of seven hours, enough to watch four average-length movies. And, for Web browsing and other Internet functions, including sending and receiving emails, viewing Google maps and YouTube videos, we got over nine hours, well above Apple’s claim of up to six hours.
In real life, of course, you will do a mix of these things, so the best gauge might be that, in our two-week test, the iPhone generally lasted all day with a typical mix of tasks."
Bold/italicized text is mine.