I ran both years.
2006 was PERFECT running weather. A little cool, but nice for running. 56 degrees at 6 am, 68 at 9 am. Clear and not humid.
2007. Crazy heat wave came in a couple of days before the race. Temps in Anaheim were over 100 the day before. We started the race at 6 am with a temp of about 78 degrees. By 9 am, it was 85. By 10 am, it was 90. Later, on race day, it reached a high of 108!! (seriously, just check
www.wunderground.com)
That said, the heat wave was an unusual weather occurrence for that area, from what everyone told me, including my brother who lives in LA.
Just for the castle medal, it is awesome! I would go for the special extra medal this year, but I have a big triathlon the week before, so can't do the DL race. darn.
As for the race course...you start through DCA, then go through DL...a lot of it after that is up and down plain city streets, so not so nice (at least the roads between the parks at WDW are landscaped...at DL it's an industrial area). Then, running through Angel Stadium is cool, then you go back through DCA and Downtown Disney to the finish. Couple of overpass hills, but otherwise flat.
Cheers!