Hi!
As others have said, if you're content to miss out on some of the rides and shows, are prepared to ignore the atmosphere (not like Disney, but it's there) and are willing rush about like a headless chicken then it's possible.
Now, if you just don't have the time and/or are absolutely not willing to pay for more than one day, I can understand the one-day option. When you've got no choice, something is better than nothing.
But really, you need one day per park in Sept., when crowds are - usually - quite manageable.
As with all the Orlando parks, to make the most of your day and ensure that you get to do your favourite ride more than once or twice, it's still highly advisable to get an early start but for a Sept. visit there's absolutely no need to pay extra for the Express Pass. My family and i were in Orlando for 23 days last Sept., 2.5 of those days in Universal, and the relatively few people using Express Passes were the group tourists who had obviously had them included in some sort of package. Sure, we queued up for some of the rides later in the day but not more than 10min or so.....There was also hardly any wait for the rollercoaster front-seats, which usually have longer lines than the lines for the seats further back!
Others will disagree with me but that was my experience last Sept. s that was my 2c worth!
