It depends on how busy the parks are and where you want to eat. Sci Fi and Prime Time at MGM pretty much always require ADRs for lunch, while Kona and WCC seldom do during slower times of the year. During busy times, you need ressies for any sort of TS meal.
yeah, after hanging out here on the restaurant board for awhile, I kind of figured as much. trying to tie down our group to make a decision is near impossible, though. we all went 5 years ago and made our ressies when we were there...how things have changed...