I have stayed onsite and enjoyed the FOTL benefit quite a bit. After I got to experience that, I swore that staying off-sight would...well, basically suck.
Then I wanted to take my cousin to Universal Studios/Islands of Adventure for the first time. Worried that the trip wouldn't be too great because we would be staying off-site, I hesitated. I ended up accepting this option or else it would be a solo-day trip, and there was no way we could experience it all.
Well, let me tell you, when we went, it was early August and the crowds were PACKED. I mean, they were more crowded than our earlier summer trips!! I was really nervous about not having FOTL again.
Turned out, in those two days, we did everything we wanted. We did Spiderman, Hulk, Dueling Dragons, Back to the Future a few times. We also did Men in Black, Twister, Earthquake, Jimmy Neutron, and Shrek 4-D once (would have done some of those more if she liked them better.

Had nothing to do with time...unless it conflicted with the Ghostbusters Show...

Which reminds me, she saw about... 4 or 5 Ghostbusters Shows and The Horror Makeup Show twice as well.
AND THIS WAS DURING THE BUSIEST TIME OF YEAR!!!!!!!!!!
September is less crowded, and let me tell you, you'll have nothing to worry about. Nothing. Nada. Zip.

Yay!
The key is to know which rides are more popular and get crowded the quickest. Also, every pass can get you an Express Pass. Good to use Express for popular rides like Shrek in order to save time. It's all about strategy!
PS - crowds are already starting to go way down...I saw the Shrek line as low as 45 minutes last Saturday!!!
