I am having trouble with it, on one route plan in particular. (This is using IE6, and I've also tried it with FF2 - have also tried re-bookmarking the applet link)
Mostly it works as usual, but one route in the south of France seems perfectly OK in Google Maps but the Gmapto GPX thingy just doesn't do it, and I get a javascript error mark in the browser border instead. Very odd. Have tried breaking the route in half and tried each half separately, but still no joy. Route not particularly long or complex. Other routes elsewhere in UK and France work as expected. Bizarre.