if you're looking for a fast sata hdd w/ a great warranty, for use on a family computer (doesn't require 100's of gb's of storage) you could spend $45 on a 80gb drive shipped at newegg or elsewhere, or you can muster up the extra $10 for the 160gb from seagate.
Find just 1 hdd of the same performance that compares in price to this hdd (~$57 after shipping).
Comparing the $/GB of a 250-300gb hdd to this 160gb drive is like comparing apples to oranges. People get these drives either because A.) They want a cheap yet fast hdd (size doesn't matter for them), or B.) They want a cheap Raid set-up.
2 of these drives in are about the same price as a 320GB SATA2 hdd (give or take a couple bucks), but when used in Raid will outperform any single SATA 16mb cache drive in file transfer.