The T-Mobile G1's lack of battery life has always been a concern, especially after we learned about its data roaming issues. Seidio's new battery combats this problem without the need for a new cover.
The 1400mAh battery adds an additional 400mAh over the OEM version, which should earn you an extra hour or so of talk time. And, as mentioned, it does not take up any additional space, so no replacement battery door is necessary. On the downside, it will set you back $43—which may be a bit more than the casual user is willing to spend. [Seidio]