Aren't they the gun that actually advertised a finish resistant to showing fingerprints?
I think I'm with CT on this one. Different guns are always mechanically interesting but I don't think the Tec 9 has enough virtues to offset the notoriety of them.
Open Bolt semi-auto Tec-9's were classified as machineguns by ATF around 1984-85. So if you see one, just walk away.
ETA - I think the original open bolt ones were called KG-9's back then. Then the closed bolt was called the KG-99; IIRC. At some point the original MFG sold out to Intratec (late '80's early '90's IIRC).
Pistol versions of SMG's and pistol version of assault rifles have never had ANY appeal to me other than they look cool. They are very difficult to hit anything with, so you end up just using them as a range hose. Worthless.