The lacie drives are just 2 (or 4) normal hard drives in a firewire box.
The build quality is a lot better than most external enclosures -thick extruded metal, and good quality connectors with secure mounting for the HDs, with some space for air circulation.
We had a 400 GB one at work which got dropped, so we took it apart. 2 200 GB WD drives. The drives aren't in RAID (they're just spanned [JBOD]) - so don't expect massive data rates even with the IEEE1394-800 interface. As an aside, we swapped the original drives out for a pair of 400 GB seagates, and it worked fine - detected straight away as a 750 GB drive.