The battery life of the Sony Ericsson Mix Walkman is pretty decent, as long as you're not hammering the Wi-Fi. General calls, a bit of light internet browsing and Walkman use will last the quoted nine hours of talk time, and we even went a good day and a half without charging it at one point. Standby time is quoted as up to 465 hours.
There is, of course, no major app or processing power to kill the battery, except for Wi-Fi. Once that's enabled, you're looking at about half the battery life.
But be thankful for that Wi-Fi, because it is certainly the best connectivity offered by the Sony Ericsson Mix Walkman. There's no 3G internet on this thing.
There is a micro USB port though, for drag-and-drop file arranging between the phone and your computer, which works just fine.