These are much better than the earlier scripts in that they are completely automatic in operation, just open a terminal in the folder containing the images and call the script with appropriate arguments, and it will run to completion and open one of the made thumbnail pages for your preview. They take about 30 minutes on a 2ghz machine for 1,000 images, and makes 6x4 pages.
I've found that you can't just copy and paste the script from the web page, the browser renders just enough of it to corrupt the code, you have to right click on the link to the page and save as, then strip the code out of the page. I'll redo that so that you can just download the files in text for in a bit. I have a lot of changes to make.