Performance is what can be expected for a typical USB 2.0 interface. With JBOD (Just a Bunch Of Disks) the two drives show up as separate volumes, and although there is no controller for RAID mirroring or striping, it would be nice to at least have the option to combine the two using spanning.
As with some other Raidsonic products, I had a difficult time finding the IB 3218 available for sale here in the states. Tagan doesn't even list the enclosure on their website yet. I did see it on some overseas sites however for around 32 Euros, which is the equivalent of about $50 US. That's probably about right, considering the similarly-featured IB 3220 enclosure can be found for $59.99, and that model has hot-swap drive trays. Given the sturdy aluminum construction, ease of use and right price, the IB 3218 should offer a good buy assuming you can find one.
OCIA.net has awarded the Icy Box IB 3218 our Seal of Approval.