I RMA'd my battery on Tuesday as mentioned in a previous thread. On the same day, I ordered the modular second battery. Today, both of the batteries are sitting in my R1 fully charged. First, let me say that Asus customer support is excellent. No hold times when you call, you speak to people who know the process and are familiar with what they sell. They are prompt and courteous. They paid for shipping and the turnaround was three days. No hassles and a very pleasant experience. Second, I bought the modular battery from Milestone PC. They seem to like dealing via e-mail, but they are prompt. Their purchasing process is pretty straightforward and they update you via e-mail at a number of points in the process so you know where things are at. If Canada Post had been more on it's toes, I would have had the battery in one day. Overall a good experience although the shipping fee is mildly outrageous. I'd recommend them, especially if you live in Toronto and can avoid the shipping fee Okay. So both batteries are in and Vista is reporting at 96% charge remaining I get 4 HOURS and 45 MINUTES of battery life. This is at FULL brightness, 50% Max processor state, wireless off and Vista doing it's annoying disk indexing in the background. The additional battery seems to add negligible weight to the unit. I'll be carrying two batteries as my normal load out and leaving the optical drive at home from now on. I'd say if mobility is important to you, consider the extra battery.