no you shouldn't need to enable anything else to start picking up clients. But, karma does not actually broadcast all ssids i don't think, it only broadcasts the ssid "pineapple" (or whatever you change it to). But when client computers are looking for access points it will act as if it were the access point.
For example, when karma is enabled, and I go to view available wireless networks on my mac, I can see every ap I have ever connected too plus the pineapple ssid. No matter which one I select it will establish a connection to the pineapple.
R u running the latest firmware 2.1.2?