We just came back from our trip September 22, 2003. There was no lines, no lines. If we would have went to Universal side first, could have seen both parks in one day!. No lines in September. One trick we did while we was there for faster rides is go through baby swap. This allowed us to see major rides like "men in black" 7 or 8 times. When there are no lines the attendants do not care.
I went with my wife, son (8), 2 daughters (12,13). We found out when the live shows like animal planet were. My 14 year old could not live without seeing that. We missed things like Beetle Juice and Fifle West show.
The Universal side closes at 5:30 and Islands of adventure closes at 8 or 9 pm. I had planned the Island of Adventure first because if it rained we could do inside rides, big mistake. We could have done it all in one day.