I've experienced Uranus transits hitting close to exact, both for me and others around me. I feel like major turning points often occur with Uranus Oppositions. This might be true of other hard aspects as well, but Oppositions tend to have the most "attracting" energy in terms of outer events, especially with a planet like Uranus that has a very sudden lightning-strike type of energy.
The delay of Saturn seems to be true as well. Someone above said the lessons come later, and that aligns with Saturn's goals, making changes after assessing what happened. I've experienced the "events" a little later than expected too, but the lessons started to come far after that. I've read that Saturn returns often take upto 20-25 degrees after the Conjunction, and I'd probably agree with that.
Pluto's effects seemed to come far earlier each time I've experienced a major transit (I've had a few). I think the approaching period (up to 3 degrees) for a major aspect to the Sun/Moon/ASC is often the worst, because if you're Plutonic, you know the feeling of the energy from a mile away, and you realize major possibly painful change is on it's way (and sometimes you're stuck in a situation and the impending doom seems worse than it ends up being).
Neptune is harder to pinpoint, because the nature of Neptune's fogginess makes it harder for you to realize that you're in a fog at all. It might take decades to realize a major Neptune transit caused you to be in some sort of trance for a long period of time in the past.
Jupiter I usually experience early, but I find the effects vary a lot by which aspect, but that might have to do with the nature of my chart, which is a bucket/t-square where half is empty, and Jupiter is highly prominent in my chart.