The device firmware records how much data was read/written and the driver displays that info. These things basically last forever though due to grade 3 enterprise SLC NAND and their wear leveling... Something like 40 Petabytes of writes for the 80GB version, so 160PB for the 320GB unit. Reliability is one of the major selling points.

I do have $3k to blow on useless stuff right now, but an IOdrive that large.... I don't know.

Yes, the 320GB is faster at writing than the 80GB by about 200MB/s.