Unfortunately, I have problems with getting this to work in Firefox (1.5) whether I use the bookmarklet or manually paste the parameter. It always generates the same kml file of a location in New York. Safari, Opera and Camino don’t have this problem! I’ll have to keep you posted of this one. .
* Note: that the resulting kml files are simply called ‘maps’ with no extension, so this may cause you grief, but it’s easily fixed by adding the extension.