First, I'm pretty sure there was a long thread on this same basic topic in the not so distant past. Maybe it was more about which rides and not TOT specifically although TOT was discussed a lot. Like a lot of these kinds of topics, this one before engendered a lot of discussion, both pro & con and some good parents vs. bad parents kind of thing as well.
Second, I think only YOU can really assess what will work for you child and what won't. So, I think you are wise to try to get a handle on others' experiences before you go.
On our Dec. '05 trip, we let you 6 & 1/2 year old pick what we would do first. She said she wanted to do TOT so we planned our first day for MGM. Not sure why she picked it, but maybe because she'd seen the TOT-themed movie on the Disney channel. Also, she likes the little frog hopper dropping ride at local carnivals. We took both girls through the TOT line not knowing whether the younger one who was 3 & 1/2 and right at the height cut-off would make it. We planned for one parent to leave w/ the younger girl if we couldn't all go. I tried to give the girls a little heads up. Although I hadn't been on the ride, I knew the general story and that the some of the queue could be a little scary for younger kids. We talked about that and our girls were prepared. The CMs ended up letting the little girl on w/o so much as a second glance. Another set of parents were right next to us and had two little boys almost identical in age to our girls. The girls were nervous, but they aren't easily deterred. When we got seated, the CM was asking something about who was ready and our little one raised her hands. Everyone got a kick out of that because ... w/ both hands up .... everyone thought she was doing the thrill-seeker-hands-in-the-air thing. The CM used that to rib all the scared adults.
Even though we'd read up on the ride, what we were not prepared for was the DARK. Not, it seems it would only make sense in hindsight, but it caught us off guard.
Also, we adults weren't prepared for how much our big ol' butts would leave the seat so we panicked a little about trying to keep a hold of our girls.
In the end ... the boys in front of us ... in the words of Chicken Little's dad ... screamed like little girls (and did somecrying, too). Our girls were pretty stoic about it. No tears. No freaking out. Both SAID they liked it; however, both said they wouldn't ride it again.
Actually, maelstrom in World Showcase ended up "scaring" the little one more and she used that as her standard against which to measure things like POC.
Later in the trip, both girls LOVED Splash & Big Thunder Mountains, and we rode them repeatedly. Our older daughter also love Primeval Whirl. So, it wasn't the "thrilling" part of the right that probably got to them, more of the setting.
Since that trip, our older daughter has come to me on her own and said she'd do TOT on the next trip. Her reasoning ... she'd be bigger/older and she'd know what to expect.
Both my husband and I REALLY enjoyed TOT and look forward to riding it again.
Good luck w/ your decision.
We are going to WDW in July, and my DD5 is set on going on the Tower of Terror. She is tall for her age and meets the minimum height requirements. We have never been to Disney before, so I know nothing about these rides. Is this something she would enjoy, or something we should save for a later trip? 
) Let your DD go through the que and let her decide. 
)
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