Samsung is now offering a 32GB low-power solid state hard drive (via Craig). These drives offer significantly better performance, use a fraction of the power, and weigh half as much. Because they're solid state, they're also more durable (which I would appreciate). No word on pricing, but I can assure you it's damn expensive.
The Flash-SSD weighs only half as much as a comparably-sized hard drive, but reads data three times faster and writes data 1.5 times faster. The SSD uses just five percent of the electricity needed to power a hard disc drive and is noiseless. Its design is free of any motor or other mechanical parts.
Samsung says a 1.8" Flash-SSD can read at speeds of up to 57Mbps and write 32Mbps, while a similar sized 1.8" HDD will perform these operations with a maximum speed of 15Mbps. Power consumptions is 0.1W (off) and 0.5W (on) compared to 1.5W on a HDD unit.
As prices become more reasonable, solid states are inevitable for mobile devices. Even 32 GB is reasonable for most mobile devices.