The Java applets in this case are actually less efficient than the Javascript feed by a good bit.
We're pretty much talking about the difference between one connection per update and one per session. But I don't see how you can work around that slow mem buildup otherwise...I'd say that's a bigger problem than the throbbing icon.. ;)
Lessee...one batch per second? How about restarting the document every 30 seconds or so? Maybe have the feed on one (invisible) frame and the display on another, and just restart the feed frame regularly. Wouldn't solve the throbber problem, but might help client memory.