I know I'm going to regret this.
I run easywdw.com - a site that gets over 850,000 visitors/month. I write the highest rated Walt Disney World guidebook on
Amazon of all time (of all time) and have visited the theme parks well over 500 times over the last five years. I can also pull up those wait times charts for any park, any day, all day, for the last couple of years. Tens of thousands of people have used my crowd calendars, cheat sheets, etc. So I have a lot of experience with this sort of thing.
FP+ has affected wait times in a variety of ways.
The biggest change is in secondary attractions that didn't historically offer FastPass+. FP+ is, in essence, priority boarding for those that have it. So if you have 1,000 people in line at Haunted Mansion and Haunted Mansion moves through 2,000 people/hour, your wait would be 30 minutes if you were the 1,001st person in line. If you have that same 1,000 people in line, but 200 of them have FP+, your wait would still be 30 minutes because you're still behind 1,000 people. The reason the wait is longer is because while you're waiting, 200 more people with FP+ arrive after you. And because they have priority boarding, they will be seated and ride before you. So instead of being behind 1,000 people, you're now behind 1,200 people and your wait is longer because of it.
FastPass+ has its biggest impact on days with higher attendance because more FP+ are distributed to more people. If there are 10,000 people all selecting 3 FP+, you have a total of 30,000 FP+. If there are 30,000 people all selecting FP+, you have 90,000 FP+. And because there are a limited number of high priority FP+ at the major attractions, the people that choose later will have fewer options and will be selecting lower priority FP+ choices because that's what's remaining in inventory. But they will still have FP+ for those low priority attractions, arrive after you, and board before you. And because of that, you will wait longer. The 4th FP+ thing has also "helped" increase waits. Just yesterday I got a 4th FP+ for Living with the Land around 1:15pm for 1:25pm-2:25pm. The posted wait was 30 minutes and there were hundreds of people in line. I boarded in under five minutes, bypassing all of those people that arrived before me. And they will wait longer because of it.
But FP+ is affecting wait times more and more on "less crowded" days because more people are privy to FP+ because Disney is making such a big deal out of it. And with 4th and subsequent FP+ opportunities via kiosk, you see more and more cases of maximum FP+ distribution, even for the lowest priority attractions. And because there is some disconnect between wait times and what FP+ are available, people are more likely to make blind decisions on which FP+ they select. Back in the days of legacy FASTPASS, you might arrive at DINOSAUR, see a 10-minute wait, and just get in line instead of pulling those FASTPASSes. Now, you have to select that DINOSAUR FP+ from a kiosk no closer than Disney Outfitters in front of the Tree of Life. And because you don't know the wait time, you might select DINOSAUR even if it has a 10-minute wait because you don't know it has a 10-minute wait. And when you arrive and see the 10-minute wait, most people are still going to use their FP+. And people in standby wait longer because all those people that arrived after them have priority boarding.
So while it might not make a lot of sense to get FP+ for Journey into Imagination, somebody will still select FP+ for that attraction because it might be the only thing left and it makes a lot more sense to get something than to get nothing. So when you show up at 1pm for Journey into Imagination and there are 100 people in front of you in standby, another 100 people might arrive with FP+ and they will all board before you. So in essence, you are waiting behind 200 people instead of 100. With legacy FASTPASS, Journey into Imagination would not have allowed priority boarding like that. And the 100 people that arrived after you would board after you, resulting in a shorter wait.
This seems like it should be easy to understand.
The other major effect FP+ has had is how quickly lines develop, particularly at secondary attractions that didn't offer FP+, but also at the priority attractions. Legacy FASTPASS return times generally started at 9:40am, then once 9:05am hit, they were distributed for 9:45am-10:45am, and after that, 9:50am-10:50am etc. So those that arrived first thing in the morning could pull legacy FASTPASS for the earliest return windows, and also had 40+ minutes to tour the legacy FASTPASS attractions before FASTPASS users began to arrive with their paper tickets around 10am. And because relatively few people were around to pull those 9:40am-10:40am FASTPASSes, you had relatively low distribution numbers and fewer people returning between 10am-11am with FASTPASSes in hand than say, 3pm-4pm.
With FP+, there will be people arriving right at 9am with FP+ because that's their first window. And while we could argue that it doesn't make any sense to use FP+ at Big Thunder Mountain at 9:15am, there will still be people doing just that because that's what was available and they "don't know any better." So if you get to Big Thunder at 9:45am and there are 100 people in front of you, you'd wait behind those 100 people under legacy FASTPASS. Maybe a handful of FASTPASS returners would get back there that soon, but it would be a negligible number. Under FP+, you have as many as a thousand people visiting Big Thunder between 9am-10am with FP+ in hand. And a lot of those FP+ returners will arrive after you and ride before you. And because of that, you will wait longer.
Those two things alone have rocked theme park touring strategy. The mornings are more of a rush and you will wait longer. And secondary attractions that historically didn't develop sizable waits until much later in the day now develop longer waits, earlier, due to FastPass+ returners.
I wrote a post around this time last year comparing posted waits before and after FP+ implementation:
http://www.easywdw.com/uncategorize...cting-wait-times-at-disney-world-attractions/. While it's no secret that posted waits aren't always indicative of actual waits, the day-to-day trends are much more telling. And when you have millions of numbers to work with, you can make some relatively definitive conclusions based on that data, in addition to the hundreds of visits that I suppose are "anecdotal" by some definitions. Not perfect conclusions, but ones based on more data and experience than you'll find anywhere else.
That's my experience based on a few hundred visits and millions of wait times, anyway.