Yes, SL3 uses a USB Dongle.
On top of that, there are reports that the v3s of SX and one of the other ones are having performance issues that have been traced back to the dongle.
I saw a thread on KVR about this recently, and I understand there is some chatter about it in the Steinberg forums. You should maybe take a look at the Steinberg forums.
Unless you're getting SL3 as a throw-in with a soundcard, you might want to consider alternatives. Steinberg products arent as Mac friendly as other software.
Help Desk