My Hyperdrive Space claims 100GB on a charge. I don't think I ever charged it on my week-long trips and it never fell below 3/4 charge. I probably only downloaded 12-15GB in a week.

It does have a quirky UI, and don't expect the 1GB/minute unless you have whatever DMA-enabled superfast cards they tested with (probably a Sandisk IV/Ducati). I got about 6min/GB with my 50x Kensington card last time I used it. I haven't tried with my newer ExtremeIII/166xcards.

With cards getting cheaper, I now have about 16GB in just a few cards, so the need for the PSD is limited to very extended trips now. If I were doing it over today, I could buy 25GB of cards for the cost of the PSD now. Of course, it's always nice to have a second copy.