I used a Velociraptor in my last PC build, but I won't use them again after that. They're not that cheap, and the performance benefits weren't that great compared to a modest HDD. After I replaced some 1.5TB Caviar Blacks in my current PC with some average 2TB drives (Caviar Blacks are just too loud -- and one of them has 5% bad sectors

), I replaced the 320GB Velociraptor with a 1.5TB drive.
Although, I do feel your pain on being addicted. I'm having to force myself to
not buy the 3TB HDD that's on sale at Newegg right now. I don't really need it, but I would
like to replace two of my 1.5TB HDDs with one 3TB drive. While the fact that I don't truly need it is holding me back (the two HDDs have about 600GB of free space each), the bigger reason is that $150 still isn't that good of a deal. I believe the first 3TB drive that I bought only cost me $120 on sale.
I wish the prices would go back down faster.