Sort of off topic-
I have seen the FN Five-seveN for sale to civilians as well. I think a lot of distributors got stuck with them so they are quietly being sold to dealers who have a letter on record that they will only sell to law enforcement and not civilians. The letter of record is a wink and nod thing that allows FN and the distributor to deny they sold a pistol that shoots AP rounds to the masses. It's something imposed by FN to curtail their potential liability. It's fallout from the gun lawsuits. -Keep in mind, even if you're right, it is expensive to defend yourself in court. There is no Federal law preventing the average person from owning one.
As I understand it, they were supposed to be a compliment to the P90 submachine-gun. They shoot the same ammo as the P90. The P90 was originally geared for soldiers who were not infantry, such as tank and artillery crews. However, few countries have opted to purchase them for their militaries. I believe the list is short (Saudi Arabia, Peru, and Thailand). Personally, I think it would be a logistical nightmare to add another caliber that isn't general issue, but to each their own.
The problem in this country is that most agencies aren't buying the P90 to replace the MP5 or the M-4 (M-16 carbine variant), so there aren't that many people picking up the "matching" pistol in an uncommon caliber. -If memory serves, the ammo is also very pricey (something like fifty cents a round).
However, if you want a pistol that can punch through a standard kevlar vest at a 100 yards, knock yourself out... It'll be interesting to see if the gun can make better headway into the market after the ban sunsets. One can only imagine it could be a popular compliment to a civilian version of the P90 (assuming FN would make such a beastie).