The split is about 50/50 right now. I've run the crawler three times in the last ~5 months and observed the transition from 1.3.2 to 1.4.2 moving along quite nicely though. After my first run, 1.4 adoption was so anemic that I was worried 1.3.2 was going to be jQuery's IE6. At this rate, it looks like 1.3.x should be a small minority by the time 1.5 rolls around.