Interesting change in trading strategy, but they will face a lot of competition in the market, where USB 2.0 HDDs and Floppy drives already exist.
PX-EH25L (250GB) seems more original but if the indicated transfer rate is also the one for HDD/Main computer seems a bit low, as its strange if the connection is via RJ and not USB 2.0.
HDDs are not the fastest (5400) but that seems ok. Another story is to look at MAX transfer rates and not at minimum sustained rates, or having the size of the cache (will it be 2 or 8 MB?).
And just one USB connection for power can be not enough, as it risks slowing down the disk's speed.
As we do not see the rear side of the devices, do they have a second connetion to grab more power? This can be important, specially for notebooks.
Can it receive an external power supply?
Besides I do prefer firewire connection (specially for video - DV) I have an external USB 2.0 HDD and it works fine but have these connections.
The external power will give you stability and help to kepp the competer cooler - as the disk contributes to increase the heat, if it grabs power from the machine - this is importante for long operation periods.
More details on PX-EH25L would be of interest, if someone can provide the info.