Given what we know of the battery performance from the new AMD Brazos platform, we're expecting to see a decent result. Furthermore, this netbook is bottom heavy, with most of the weight balanced around a massive 10.8V, ~5100mAh battery.
Power consumption figures also show at least twice that of the AMD C-50 processor powered netbook. This is in line with TDP figures, but thanks to that big battery on the dm1, you're still getting pretty decent battery life at 278 minutes (or 4 hours and 38 minutes).
The portability index test is a simple one, and for those who haven't come across our test before, it basically takes the battery uptime of the netbook, which then gets divided by the product of the netbook's weight and volume. What you get is a ratio that shows how portable a device is. While the ratio does give a good indication of a notebook's portability, sometimes common sense must be in place to interpret the results. A heavy battery with good battery life may give you a notebook with a high score, but you might not want to carry the notebook around too much. Similarly, a lighter notebook with a weaker battery life (but still decent enough) may post a high score, but the battery life may not be enough.
The HP Pavilion dm1, despite feeling heavy in our hands, only checks in at a comfy 1.53kg. You already know the battery life is pretty good, so the dm1's score of 1.573 should not be surprising. So, in our opinion, yes, the dm1 is quite the portable device.