OK, I have some (I hope) good news. That link above was nothing to do with Artemis, but rather showed an infection found that just happened to be called Artemis. The real thing is finally to be released soon, but please note that this applies only to the retail versions, i.e. those bought either directly from McAfee, or off the shelf, not yet those supplied by ISP's such as Comcast, etc., and only to Security Center 9.x - 2009. These updates take time to filter through the network so may not occur for some time.
Geraner, I owe you an apology. Apparently that download will enable Artemis, with a proviso. Any Security Center version less than 9.3 (which does have it already) will not be configurable, i.e. there wont be a switch to turn it on or off. The only way to stop it in that case is to uninstall it. There is a separate entry for it in Control Panel.
The update of Security Center 9 to 9.3 is slowly being released. At present it is only going out to the Australian market but the rest will follow in quick order, hopefully.
Once Artemis is installed and active any unknown infection detected by VirusScan will be labelled as Generic!Artemis and sent automatically to McAfee for further analysis.
This is what we were told today on our conference call with McAfee management.