Due to a relatively small 1500 mAh battery and the need to light up two displays, battery life wasn't great. The talk time rating of three hours is fairly typical, but using the phone for everyday use (browsing the Web occasionally, checking e-mail, and sending text messages) only netted around six hours of usage.
You can extend the battery life using an app like Juice Defender, which disables the 4G connection for background usage. (To enable the connection, you just tap an option for short-term usage.)
While plenty of phones are still rocking Gingerbread, we couldn't help but think of all the ways the DoublePlay could have benefited from it. Being stuck on Gingerbread means Android Beam is not available - a tool that lets you send YouTube video links, Web site bookmarks, and your contacts by tapping phones together.
The DoublePlay does support Wi-Fi and Bluetooth 3.0, but doesn't support Bluetooth 4.0, the new standard that uses lower power transmissions. The DoublePlay also does not support Bluetooth HDP, the new standard included with ICS that lets you connect to heart rate monitors, step counters, and workout machines at the gym.
The phone works with the T-Mobile 4G network in the US for theoretical speeds of about 14.4Mbps, but a real-world throughput of more like 3-4Mbps. (The speed of your connection depends greatly on where you are, other users who are connected, et al.)