The other night I downloaded Java 6 Update 10 (JDK) and installed it on my Windows Vista laptop to test drive the new applets plugin. I found that some applets show off the speedy startup time better than others. For example, I would say that every one of the applets at Applet Depot loads and is usable nearly instantaneously. Interestingly, the DotToDot applet crashed Firefox 3 many times, but works now?
On the other hand, every one of Report Mill's JavaFX Gallery applets take a good 10-30 seconds or longer to load. I have to watch the orange Java logo and progress bar while they load. Even after they load, some of them show a blank screen for 10+ seconds. What's different? 814KB of .jar dependencies. I wonder if the javafxrt.jar etc. are obsolete now with compiled JavaFX Script? That would cut out a lot of download time.
The progress bar in the orange Java logo indicates how much of the applet and dependencies have been downloaded so far. I know you can replace the orange Java logo with a custom animated GIF, but I don't know how you would make it interact with the applet plugin to be able to draw a progress bar like that.